kernel/params.c | 29 +++++++++++++---------------- 1 file changed, 13 insertions(+), 16 deletions(-)
Add the __counted_by compiler attribute to the flexible array member
attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.
Increment num before adding a new param_attribute to the attrs array and
adjust the array index accordingly. Increment num immediately after the
first reallocation such that the reallocation for the NULL terminator
only needs to add 1 (instead of 2) to mk->mp->num.
Use struct_size() instead of manually calculating the size for the
reallocation.
Use krealloc_array() for the additional NULL terminator.
Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
---
Changes in v2:
- Use krealloc_array() as suggested by Andy Shevchenko
- Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/
---
kernel/params.c | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/kernel/params.c b/kernel/params.c
index 2e447f8ae183..5f6643676697 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -551,7 +551,7 @@ struct module_param_attrs
{
unsigned int num;
struct attribute_group grp;
- struct param_attribute attrs[];
+ struct param_attribute attrs[] __counted_by(num);
};
#ifdef CONFIG_SYSFS
@@ -651,35 +651,32 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
}
/* Enlarge allocations. */
- new_mp = krealloc(mk->mp,
- sizeof(*mk->mp) +
- sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
+ new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
GFP_KERNEL);
if (!new_mp)
return -ENOMEM;
mk->mp = new_mp;
+ mk->mp->num++;
/* Extra pointer for NULL terminator */
- new_attrs = krealloc(mk->mp->grp.attrs,
- sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
- GFP_KERNEL);
+ new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
+ sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
if (!new_attrs)
return -ENOMEM;
mk->mp->grp.attrs = new_attrs;
/* Tack new one on the end. */
- memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
- sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
- mk->mp->attrs[mk->mp->num].param = kp;
- mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
+ memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
+ sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
+ mk->mp->attrs[mk->mp->num - 1].param = kp;
+ mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
/* Do not allow runtime DAC changes to make param writable. */
if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
- mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
+ mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
else
- mk->mp->attrs[mk->mp->num].mattr.store = NULL;
- mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
- mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
- mk->mp->num++;
+ mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
+ mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
+ mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;
/* Fix up all the pointers, since krealloc can move us */
for (i = 0; i < mk->mp->num; i++)
--
2.46.0Hi Thorsten,
On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote:
> Add the __counted_by compiler attribute to the flexible array member
> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
>
> Increment num before adding a new param_attribute to the attrs array and
> adjust the array index accordingly. Increment num immediately after the
> first reallocation such that the reallocation for the NULL terminator
> only needs to add 1 (instead of 2) to mk->mp->num.
>
> Use struct_size() instead of manually calculating the size for the
> reallocation.
>
> Use krealloc_array() for the additional NULL terminator.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
> ---
> Changes in v2:
> - Use krealloc_array() as suggested by Andy Shevchenko
> - Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/
> ---
> kernel/params.c | 29 +++++++++++++----------------
> 1 file changed, 13 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/params.c b/kernel/params.c
> index 2e447f8ae183..5f6643676697 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -551,7 +551,7 @@ struct module_param_attrs
> {
> unsigned int num;
> struct attribute_group grp;
> - struct param_attribute attrs[];
> + struct param_attribute attrs[] __counted_by(num);
> };
>
> #ifdef CONFIG_SYSFS
> @@ -651,35 +651,32 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
> }
>
> /* Enlarge allocations. */
> - new_mp = krealloc(mk->mp,
> - sizeof(*mk->mp) +
> - sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
> + new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
> GFP_KERNEL);
> if (!new_mp)
> return -ENOMEM;
> mk->mp = new_mp;
> + mk->mp->num++;
>
> /* Extra pointer for NULL terminator */
> - new_attrs = krealloc(mk->mp->grp.attrs,
> - sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
> - GFP_KERNEL);
> + new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
> + sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
> if (!new_attrs)
> return -ENOMEM;
> mk->mp->grp.attrs = new_attrs;
>
> /* Tack new one on the end. */
> - memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
> - sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
> - mk->mp->attrs[mk->mp->num].param = kp;
> - mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
> + memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
> + sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
> + mk->mp->attrs[mk->mp->num - 1].param = kp;
> + mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
> /* Do not allow runtime DAC changes to make param writable. */
> if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
> - mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
> + mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
> else
> - mk->mp->attrs[mk->mp->num].mattr.store = NULL;
> - mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
> - mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
> - mk->mp->num++;
> + mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;
>
> /* Fix up all the pointers, since krealloc can move us */
> for (i = 0; i < mk->mp->num; i++)
> --
> 2.46.0
>
I just bisected this change to a fortify failure that I see with a
couple different ARM configurations when built with a version of clang
that supports __counted_by(). I can reproduce this with:
$ curl -LSso .config https://gist.github.com/nathanchance/6df4bd2ab4c4418020b3ed5417ef4f80/raw/758abf666dfe8c76e0f16735f336849ea47ef791/.config
$ make -skj"$(nproc)" ARCH=arm LLVM=1 olddefconfig zImage
$ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm-rootfs.cpio.zst | zstd -d >rootfs.cpio
$ qemu-system-arm \
-display none \
-nodefaults \
-no-reboot \
-machine virt \
-append 'console=ttyAMA0 earlycon' \
-kernel arch/arm/boot/zImage \
-initrd rootfs.cpio \
-m 512m \
-serial mon:stdio
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 6.11.0-rc4+ (nathan@thelio-3990X) (ClangBuiltLinux clang version 19.1.0-rc4 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87), ClangBuiltLinux LLD 19.1.0 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87)) #1 SMP Fri Sep 13 09:36:38 MST 2024
...
[ 0.623959] ------------[ cut here ]------------
[ 0.624158] WARNING: CPU: 0 PID: 1 at lib/string_helpers.c:1030 __fortify_report+0x64/0x6c
[ 0.625050] memset: detected buffer overflow: 32 byte write of buffer size 0
[ 0.625297] Modules linked in:
[ 0.625712] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc4+ #1
[ 0.626008] Hardware name: Generic DT based system
[ 0.626274] Call trace:
[ 0.626342] unwind_backtrace from show_stack+0x28/0x2c
[ 0.626690] show_stack from dump_stack_lvl+0x34/0x70
[ 0.626936] dump_stack_lvl from __warn+0xe0/0x200
[ 0.627100] __warn from warn_slowpath_fmt+0xc8/0x194
[ 0.627335] warn_slowpath_fmt from __fortify_report+0x64/0x6c
[ 0.627551] __fortify_report from __fortify_panic+0x8/0xc
[ 0.627739] __fortify_panic from add_sysfs_param+0x224/0x228
[ 0.627927] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
[ 0.628206] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
[ 0.628412] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
[ 0.628649] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
[ 0.628869] do_one_initcall from do_initcall_level+0x9c/0x104
[ 0.629068] do_initcall_level from do_initcalls+0x74/0xb0
[ 0.629254] do_initcalls from kernel_init_freeable+0x10c/0x158
[ 0.629452] kernel_init_freeable from kernel_init+0x20/0x1cc
[ 0.629654] kernel_init from ret_from_fork+0x14/0x28
[ 0.629872] Exception stack(0xe080dfb0 to 0xe080dff8)
[ 0.630108] dfa0: 00000000 00000000 00000000 00000000
[ 0.630391] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 0.630656] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 0.631064] ---[ end trace 0000000000000000 ]---
[ 0.631800] ------------[ cut here ]------------
[ 0.631989] kernel BUG at lib/string_helpers.c:1037!
[ 0.632175] Internal error: Oops - BUG: 0 [#1] SMP ARM
[ 0.632472] Modules linked in:
[ 0.632761] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.11.0-rc4+ #1
[ 0.633077] Tainted: [W]=WARN
[ 0.633186] Hardware name: Generic DT based system
[ 0.633357] PC is at __fortify_panic+0x8/0xc
[ 0.633521] LR is at __warn+0x16c/0x200
[ 0.633668] pc : [<c0f6daa8>] lr : [<c035300c>] psr: 60000013
[ 0.633878] sp : e080db98 ip : 00000000 fp : e080dbb8
[ 0.634059] r10: 6e72656b r9 : 006c656e r8 : c1000009
[ 0.634240] r7 : fffffff4 r6 : c135947c r5 : c13d5ebc r4 : c2466f00
[ 0.634470] r3 : 00000200 r2 : 00000000 r1 : 244cee50 r0 : 244cee50
[ 0.634738] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
[ 0.634987] Control: 10c5387d Table: 423ec06a DAC: 00000051
[ 0.635206] Register r0 information: non-paged memory
[ 0.635559] Register r1 information: non-paged memory
[ 0.635745] Register r2 information: NULL pointer
[ 0.635917] Register r3 information: non-paged memory
[ 0.636100] Register r4 information: slab kmalloc-64 start c2466f00 pointer offset 0 size 64
[ 0.636772] Register r5 information: non-slab/vmalloc memory
[ 0.637001] Register r6 information: non-slab/vmalloc memory
[ 0.637205] Register r7 information: non-paged memory
[ 0.637385] Register r8 information: non-slab/vmalloc memory
[ 0.637597] Register r9 information: non-paged memory
[ 0.637791] Register r10 information: non-paged memory
[ 0.637977] Register r11 information: 2-page vmalloc region starting at 0xe080c000 allocated at copy_process+0x17c/0xf18
[ 0.638382] Register r12 information: NULL pointer
[ 0.638569] Process swapper/0 (pid: 1, stack limit = 0x8a022d6d)
[ 0.639040] Stack: (0xe080db98 to 0xe080e000)
[ 0.639194] db80: e080dbb8 c037f5f8
[ 0.639462] dba0: c2466f00 c13d5ebc 00000000 c1000009 e080dbd8 6e72656b e080dbd0 c151d860
[ 0.639728] dbc0: c13d5ebc c13d6dbc 00000000 6e72656b e080dc38 c151d6d8 6e72656b 00006c65
[ 0.639993] dbe0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 0.640261] dc00: 00000000 00000000 00000000 00000000 00000000 00000000 244cee50 c1655918
[ 0.640531] dc20: c215c200 c21f9300 c170f458 c151d4f8 00000000 00000000 e080dc40 c151d528
[ 0.640795] dc40: e080df40 c0302398 5e4e6cd4 ef580029 00000000 00000000 00000000 00000000
[ 0.641067] dc60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 0.641330] dc80: 00000000 00000000 00000000 00000000 ffffffff 00000000 c18926ac 00000080
[ 0.641599] dca0: 000000b0 c061cb68 debbd794 debbd794 00000000 c21fd000 e080dce8 c061cb68
[ 0.641863] dcc0: 244cee50 00000001 00000801 debbd794 00000000 00000801 c1892640 00000000
[ 0.642126] dce0: c1893440 e080ddd0 e080ddb0 c061e2ec deb63e40 deb63e5c 00000000 00052cc0
[ 0.642390] dd00: 00000001 00000001 000000b0 00000001 00000000 00000000 00000000 00000064
[ 0.642657] dd20: 0000006c 00000080 00000001 e080ddd0 00000000 00000000 00000000 00000001
[ 0.642923] dd40: 00000000 00000000 00000000 00000001 00000000 00000000 00000001 00000000
[ 0.643187] dd60: c1892930 00000000 00000000 244cee50 00000000 00000000 00000000 00000000
[ 0.643451] dd80: 00000801 7ffe0000 c1892640 c0b3c530 244cee50 00000000 00052cc0 00000001
[ 0.643724] dda0: 00000008 00000001 00052cc0 00000000 e080de08 c061cddc 00000820 c0775f50
[ 0.643992] ddc0: 00000000 c215c200 00000000 00052cc0 c1893440 00000000 c1893440 244cee50
[ 0.644259] dde0: 00000020 debbd794 7ffe0000 c062c97c c21329c0 debbd794 0000000e 00000020
[ 0.644532] de00: 00000080 7ffe0000 e080de40 c062c97c c20a763c 00000020 e080de28 c0f74fc0
[ 0.644800] de20: 244cee50 00000000 00000080 c2133e80 00000000 7fff0000 c21329c0 deb64100
[ 0.645066] de40: e080dea0 c062a584 c21c1180 c17cb818 0fffffff 00000001 e080ded4 c0f655d8
[ 0.645330] de60: 00000000 00000001 c2132a48 ffffffff 00000000 c0f43544 ffff0a01 c0f71f18
[ 0.645592] de80: e080df20 c0f71f18 244cee50 c21c1180 00000cc0 e080ded4 00000079 00000000
[ 0.645857] dea0: 0fffffff 00000001 00000000 c0f43544 c071ca3c 00000003 00000dc0 00000000
[ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
[ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
[ 0.646391] dee0: 00000000 00000000 000000c0 c13d6dbc 00000000 c037e2ec 000000c0 c037e328
[ 0.646663] df00: e080df40 c037e328 c21fd600 00000000 c12e093d c13d5ebc 00000000 244cee50
[ 0.646929] df20: 244cee50 c1655918 c1655aa0 c21f9300 deffff00 c13578a8 00000000 00000000
[ 0.647197] df40: e080df68 c1501898 00000007 00000007 00000000 c1501900 00000019 c21f9300
[ 0.647462] df60: 00000007 00000000 e080df88 c15017c0 c2143a00 c215c200 00000000 00000000
[ 0.647736] df80: 00000000 00000000 e080df98 c150163c 00000000 c0f6fa60 e080dfa8 c0f6fa80
[ 0.648006] dfa0: 00000000 00000000 00000000 c030016c 00000000 00000000 00000000 00000000
[ 0.648273] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 0.648536] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[ 0.648801] Call trace:
[ 0.648840] __fortify_panic from add_sysfs_param+0x224/0x228
[ 0.649129] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
[ 0.649348] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
[ 0.649572] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
[ 0.649801] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
[ 0.650021] do_one_initcall from do_initcall_level+0x9c/0x104
[ 0.650223] do_initcall_level from do_initcalls+0x74/0xb0
[ 0.650412] do_initcalls from kernel_init_freeable+0x10c/0x158
[ 0.650612] kernel_init_freeable from kernel_init+0x20/0x1cc
[ 0.650810] kernel_init from ret_from_fork+0x14/0x28
[ 0.650984] Exception stack(0xe080dfb0 to 0xe080dff8)
[ 0.651164] dfa0: 00000000 00000000 00000000 00000000
[ 0.651427] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[ 0.651697] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
[ 0.652032] Code: e8bd4bf0 eae457a7 e92d4800 ebe4aaef (e7f001f2)
[ 0.652584] ---[ end trace 0000000000000000 ]---
[ 0.652825] note: swapper/0[1] exited with irqs disabled
[ 0.653314] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[ 0.654033] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
I haven't had a chance to really look over this too much but I figured I
would get the report out sooner rather than later, especially with the
merge window being around the corner. If there is any other information
I can provide or patches I can test, I am more than happy to do so.
Cheers,
Nathan
# bad: [57f962b956f1d116cd64d5c406776c4975de549d] Add linux-next specific files for 20240912
# good: [77f587896757708780a7e8792efe62939f25a5ab] Merge tag 'arm-fixes-6.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
git bisect start '57f962b956f1d116cd64d5c406776c4975de549d' '77f587896757708780a7e8792efe62939f25a5ab'
# good: [5e6a31306949eb18be8d6dc7ad6c42f8bea8e743] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
git bisect good 5e6a31306949eb18be8d6dc7ad6c42f8bea8e743
# bad: [9802faa85f4ccbc8cc0893fe76b939a9c56b9e62] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git
git bisect bad 9802faa85f4ccbc8cc0893fe76b939a9c56b9e62
# good: [793a135214a81488066fb8ccecbd4f182c416326] drm/xe/mmio: Drop compatibility macros
git bisect good 793a135214a81488066fb8ccecbd4f182c416326
# good: [d8bfeb4282b1c55342d2dd946eaf00f4f13785db] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394.git
git bisect good d8bfeb4282b1c55342d2dd946eaf00f4f13785db
# bad: [f5315deb662e813be5fa93f2b67d46fe9fcd383c] Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git
git bisect bad f5315deb662e813be5fa93f2b67d46fe9fcd383c
# good: [4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0] ASoC: dt-bindings: amlogic,axg-sound-card: document clocks property
git bisect good 4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0
# bad: [2ca98b409c36e91bb359a2997f4a7810e799bd62] Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git
git bisect bad 2ca98b409c36e91bb359a2997f4a7810e799bd62
# good: [d39b510a145a4766906cd49177695913d6e6bfd2] Add audio support for the MediaTek Genio 350-evk
git bisect good d39b510a145a4766906cd49177695913d6e6bfd2
# good: [43fbb2c702663d7af844ee952aec224a0e059e26] ASoC: loongson: Simplify code formatting
git bisect good 43fbb2c702663d7af844ee952aec224a0e059e26
# good: [0b0aa67baa8904e3c1e13be48a2ca125f59ead3d] ASoC: amd: acp: remove MODULE_ALIAS for sof based generic machine driver
git bisect good 0b0aa67baa8904e3c1e13be48a2ca125f59ead3d
# good: [8905d39085c60a13d47bd07d2766bfdde933cc8d] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git
git bisect good 8905d39085c60a13d47bd07d2766bfdde933cc8d
# good: [907fa79d787f6f762c0afb67b8b02be8ed1f7bd2] MAINTAINERS: scale modules with more reviewers
git bisect good 907fa79d787f6f762c0afb67b8b02be8ed1f7bd2
# bad: [e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7] module: abort module loading when sysfs setup suffer errors
git bisect bad e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7
# bad: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
git bisect bad 7125cb974977aa80959817548b5221314fe46bc0
# first bad commit: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
Hi Nathan,
> On 13. Sep 2024, at 18:46, Nathan Chancellor <nathan@kernel.org> wrote:
>
> Hi Thorsten,
>
> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote:
>> Add the __counted_by compiler attribute to the flexible array member
>> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
>> CONFIG_FORTIFY_SOURCE.
>>
>> Increment num before adding a new param_attribute to the attrs array and
>> adjust the array index accordingly. Increment num immediately after the
>> first reallocation such that the reallocation for the NULL terminator
>> only needs to add 1 (instead of 2) to mk->mp->num.
>>
>> Use struct_size() instead of manually calculating the size for the
>> reallocation.
>>
>> Use krealloc_array() for the additional NULL terminator.
>>
>> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
>> ---
>> Changes in v2:
>> - Use krealloc_array() as suggested by Andy Shevchenko
>> - Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/
>> ---
>> kernel/params.c | 29 +++++++++++++----------------
>> 1 file changed, 13 insertions(+), 16 deletions(-)
>>
>> diff --git a/kernel/params.c b/kernel/params.c
>> index 2e447f8ae183..5f6643676697 100644
>> --- a/kernel/params.c
>> +++ b/kernel/params.c
>> @@ -551,7 +551,7 @@ struct module_param_attrs
>> {
>> unsigned int num;
>> struct attribute_group grp;
>> - struct param_attribute attrs[];
>> + struct param_attribute attrs[] __counted_by(num);
>> };
>>
>> #ifdef CONFIG_SYSFS
>> @@ -651,35 +651,32 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
>> }
>>
>> /* Enlarge allocations. */
>> - new_mp = krealloc(mk->mp,
>> - sizeof(*mk->mp) +
>> - sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
>> + new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
>> GFP_KERNEL);
>> if (!new_mp)
>> return -ENOMEM;
>> mk->mp = new_mp;
>> + mk->mp->num++;
>>
>> /* Extra pointer for NULL terminator */
>> - new_attrs = krealloc(mk->mp->grp.attrs,
>> - sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
>> - GFP_KERNEL);
>> + new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
>> + sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
>> if (!new_attrs)
>> return -ENOMEM;
>> mk->mp->grp.attrs = new_attrs;
>>
>> /* Tack new one on the end. */
>> - memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
>> - sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
>> - mk->mp->attrs[mk->mp->num].param = kp;
>> - mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
>> + memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
>> + sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
>> + mk->mp->attrs[mk->mp->num - 1].param = kp;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
>> /* Do not allow runtime DAC changes to make param writable. */
>> if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
>> - mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
>> else
>> - mk->mp->attrs[mk->mp->num].mattr.store = NULL;
>> - mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
>> - mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
>> - mk->mp->num++;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
>> + mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;
>>
>> /* Fix up all the pointers, since krealloc can move us */
>> for (i = 0; i < mk->mp->num; i++)
>> --
>> 2.46.0
>>
>
> I just bisected this change to a fortify failure that I see with a
> couple different ARM configurations when built with a version of clang
> that supports __counted_by(). I can reproduce this with:
>
> $ curl -LSso .config https://gist.github.com/nathanchance/6df4bd2ab4c4418020b3ed5417ef4f80/raw/758abf666dfe8c76e0f16735f336849ea47ef791/.config
>
> $ make -skj"$(nproc)" ARCH=arm LLVM=1 olddefconfig zImage
>
> $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm-rootfs.cpio.zst | zstd -d >rootfs.cpio
>
> $ qemu-system-arm \
> -display none \
> -nodefaults \
> -no-reboot \
> -machine virt \
> -append 'console=ttyAMA0 earlycon' \
> -kernel arch/arm/boot/zImage \
> -initrd rootfs.cpio \
> -m 512m \
> -serial mon:stdio
> [ 0.000000] Booting Linux on physical CPU 0x0
> [ 0.000000] Linux version 6.11.0-rc4+ (nathan@thelio-3990X) (ClangBuiltLinux clang version 19.1.0-rc4 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87), ClangBuiltLinux LLD 19.1.0 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87)) #1 SMP Fri Sep 13 09:36:38 MST 2024
> ...
> [ 0.623959] ------------[ cut here ]------------
> [ 0.624158] WARNING: CPU: 0 PID: 1 at lib/string_helpers.c:1030 __fortify_report+0x64/0x6c
> [ 0.625050] memset: detected buffer overflow: 32 byte write of buffer size 0
> [ 0.625297] Modules linked in:
> [ 0.625712] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc4+ #1
> [ 0.626008] Hardware name: Generic DT based system
> [ 0.626274] Call trace:
> [ 0.626342] unwind_backtrace from show_stack+0x28/0x2c
> [ 0.626690] show_stack from dump_stack_lvl+0x34/0x70
> [ 0.626936] dump_stack_lvl from __warn+0xe0/0x200
> [ 0.627100] __warn from warn_slowpath_fmt+0xc8/0x194
> [ 0.627335] warn_slowpath_fmt from __fortify_report+0x64/0x6c
> [ 0.627551] __fortify_report from __fortify_panic+0x8/0xc
> [ 0.627739] __fortify_panic from add_sysfs_param+0x224/0x228
> [ 0.627927] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
> [ 0.628206] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
> [ 0.628412] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
> [ 0.628649] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
> [ 0.628869] do_one_initcall from do_initcall_level+0x9c/0x104
> [ 0.629068] do_initcall_level from do_initcalls+0x74/0xb0
> [ 0.629254] do_initcalls from kernel_init_freeable+0x10c/0x158
> [ 0.629452] kernel_init_freeable from kernel_init+0x20/0x1cc
> [ 0.629654] kernel_init from ret_from_fork+0x14/0x28
> [ 0.629872] Exception stack(0xe080dfb0 to 0xe080dff8)
> [ 0.630108] dfa0: 00000000 00000000 00000000 00000000
> [ 0.630391] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.630656] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.631064] ---[ end trace 0000000000000000 ]---
> [ 0.631800] ------------[ cut here ]------------
> [ 0.631989] kernel BUG at lib/string_helpers.c:1037!
> [ 0.632175] Internal error: Oops - BUG: 0 [#1] SMP ARM
> [ 0.632472] Modules linked in:
> [ 0.632761] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.11.0-rc4+ #1
> [ 0.633077] Tainted: [W]=WARN
> [ 0.633186] Hardware name: Generic DT based system
> [ 0.633357] PC is at __fortify_panic+0x8/0xc
> [ 0.633521] LR is at __warn+0x16c/0x200
> [ 0.633668] pc : [<c0f6daa8>] lr : [<c035300c>] psr: 60000013
> [ 0.633878] sp : e080db98 ip : 00000000 fp : e080dbb8
> [ 0.634059] r10: 6e72656b r9 : 006c656e r8 : c1000009
> [ 0.634240] r7 : fffffff4 r6 : c135947c r5 : c13d5ebc r4 : c2466f00
> [ 0.634470] r3 : 00000200 r2 : 00000000 r1 : 244cee50 r0 : 244cee50
> [ 0.634738] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
> [ 0.634987] Control: 10c5387d Table: 423ec06a DAC: 00000051
> [ 0.635206] Register r0 information: non-paged memory
> [ 0.635559] Register r1 information: non-paged memory
> [ 0.635745] Register r2 information: NULL pointer
> [ 0.635917] Register r3 information: non-paged memory
> [ 0.636100] Register r4 information: slab kmalloc-64 start c2466f00 pointer offset 0 size 64
> [ 0.636772] Register r5 information: non-slab/vmalloc memory
> [ 0.637001] Register r6 information: non-slab/vmalloc memory
> [ 0.637205] Register r7 information: non-paged memory
> [ 0.637385] Register r8 information: non-slab/vmalloc memory
> [ 0.637597] Register r9 information: non-paged memory
> [ 0.637791] Register r10 information: non-paged memory
> [ 0.637977] Register r11 information: 2-page vmalloc region starting at 0xe080c000 allocated at copy_process+0x17c/0xf18
> [ 0.638382] Register r12 information: NULL pointer
> [ 0.638569] Process swapper/0 (pid: 1, stack limit = 0x8a022d6d)
> [ 0.639040] Stack: (0xe080db98 to 0xe080e000)
> [ 0.639194] db80: e080dbb8 c037f5f8
> [ 0.639462] dba0: c2466f00 c13d5ebc 00000000 c1000009 e080dbd8 6e72656b e080dbd0 c151d860
> [ 0.639728] dbc0: c13d5ebc c13d6dbc 00000000 6e72656b e080dc38 c151d6d8 6e72656b 00006c65
> [ 0.639993] dbe0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.640261] dc00: 00000000 00000000 00000000 00000000 00000000 00000000 244cee50 c1655918
> [ 0.640531] dc20: c215c200 c21f9300 c170f458 c151d4f8 00000000 00000000 e080dc40 c151d528
> [ 0.640795] dc40: e080df40 c0302398 5e4e6cd4 ef580029 00000000 00000000 00000000 00000000
> [ 0.641067] dc60: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.641330] dc80: 00000000 00000000 00000000 00000000 ffffffff 00000000 c18926ac 00000080
> [ 0.641599] dca0: 000000b0 c061cb68 debbd794 debbd794 00000000 c21fd000 e080dce8 c061cb68
> [ 0.641863] dcc0: 244cee50 00000001 00000801 debbd794 00000000 00000801 c1892640 00000000
> [ 0.642126] dce0: c1893440 e080ddd0 e080ddb0 c061e2ec deb63e40 deb63e5c 00000000 00052cc0
> [ 0.642390] dd00: 00000001 00000001 000000b0 00000001 00000000 00000000 00000000 00000064
> [ 0.642657] dd20: 0000006c 00000080 00000001 e080ddd0 00000000 00000000 00000000 00000001
> [ 0.642923] dd40: 00000000 00000000 00000000 00000001 00000000 00000000 00000001 00000000
> [ 0.643187] dd60: c1892930 00000000 00000000 244cee50 00000000 00000000 00000000 00000000
> [ 0.643451] dd80: 00000801 7ffe0000 c1892640 c0b3c530 244cee50 00000000 00052cc0 00000001
> [ 0.643724] dda0: 00000008 00000001 00052cc0 00000000 e080de08 c061cddc 00000820 c0775f50
> [ 0.643992] ddc0: 00000000 c215c200 00000000 00052cc0 c1893440 00000000 c1893440 244cee50
> [ 0.644259] dde0: 00000020 debbd794 7ffe0000 c062c97c c21329c0 debbd794 0000000e 00000020
> [ 0.644532] de00: 00000080 7ffe0000 e080de40 c062c97c c20a763c 00000020 e080de28 c0f74fc0
> [ 0.644800] de20: 244cee50 00000000 00000080 c2133e80 00000000 7fff0000 c21329c0 deb64100
> [ 0.645066] de40: e080dea0 c062a584 c21c1180 c17cb818 0fffffff 00000001 e080ded4 c0f655d8
> [ 0.645330] de60: 00000000 00000001 c2132a48 ffffffff 00000000 c0f43544 ffff0a01 c0f71f18
> [ 0.645592] de80: e080df20 c0f71f18 244cee50 c21c1180 00000cc0 e080ded4 00000079 00000000
> [ 0.645857] dea0: 0fffffff 00000001 00000000 c0f43544 c071ca3c 00000003 00000dc0 00000000
> [ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
> [ 0.646121] dec0: 00000cc0 00000000 0003ffff 80000053 c21fd66c c17cb818 00000000 00000000
> [ 0.646391] dee0: 00000000 00000000 000000c0 c13d6dbc 00000000 c037e2ec 000000c0 c037e328
> [ 0.646663] df00: e080df40 c037e328 c21fd600 00000000 c12e093d c13d5ebc 00000000 244cee50
> [ 0.646929] df20: 244cee50 c1655918 c1655aa0 c21f9300 deffff00 c13578a8 00000000 00000000
> [ 0.647197] df40: e080df68 c1501898 00000007 00000007 00000000 c1501900 00000019 c21f9300
> [ 0.647462] df60: 00000007 00000000 e080df88 c15017c0 c2143a00 c215c200 00000000 00000000
> [ 0.647736] df80: 00000000 00000000 e080df98 c150163c 00000000 c0f6fa60 e080dfa8 c0f6fa80
> [ 0.648006] dfa0: 00000000 00000000 00000000 c030016c 00000000 00000000 00000000 00000000
> [ 0.648273] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.648536] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
> [ 0.648801] Call trace:
> [ 0.648840] __fortify_panic from add_sysfs_param+0x224/0x228
> [ 0.649129] add_sysfs_param from kernel_add_sysfs_param+0x5c/0xa0
> [ 0.649348] kernel_add_sysfs_param from param_sysfs_builtin+0xf4/0x130
> [ 0.649572] param_sysfs_builtin from param_sysfs_builtin_init+0x30/0x38
> [ 0.649801] param_sysfs_builtin_init from do_one_initcall+0xd0/0x2d4
> [ 0.650021] do_one_initcall from do_initcall_level+0x9c/0x104
> [ 0.650223] do_initcall_level from do_initcalls+0x74/0xb0
> [ 0.650412] do_initcalls from kernel_init_freeable+0x10c/0x158
> [ 0.650612] kernel_init_freeable from kernel_init+0x20/0x1cc
> [ 0.650810] kernel_init from ret_from_fork+0x14/0x28
> [ 0.650984] Exception stack(0xe080dfb0 to 0xe080dff8)
> [ 0.651164] dfa0: 00000000 00000000 00000000 00000000
> [ 0.651427] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 0.651697] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 0.652032] Code: e8bd4bf0 eae457a7 e92d4800 ebe4aaef (e7f001f2)
> [ 0.652584] ---[ end trace 0000000000000000 ]---
> [ 0.652825] note: swapper/0[1] exited with irqs disabled
> [ 0.653314] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> [ 0.654033] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
>
> I haven't had a chance to really look over this too much but I figured I
> would get the report out sooner rather than later, especially with the
> merge window being around the corner. If there is any other information
> I can provide or patches I can test, I am more than happy to do so.
>
> Cheers,
> Nathan
>
> # bad: [57f962b956f1d116cd64d5c406776c4975de549d] Add linux-next specific files for 20240912
> # good: [77f587896757708780a7e8792efe62939f25a5ab] Merge tag 'arm-fixes-6.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
> git bisect start '57f962b956f1d116cd64d5c406776c4975de549d' '77f587896757708780a7e8792efe62939f25a5ab'
> # good: [5e6a31306949eb18be8d6dc7ad6c42f8bea8e743] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git
> git bisect good 5e6a31306949eb18be8d6dc7ad6c42f8bea8e743
> # bad: [9802faa85f4ccbc8cc0893fe76b939a9c56b9e62] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-power-supply.git
> git bisect bad 9802faa85f4ccbc8cc0893fe76b939a9c56b9e62
> # good: [793a135214a81488066fb8ccecbd4f182c416326] drm/xe/mmio: Drop compatibility macros
> git bisect good 793a135214a81488066fb8ccecbd4f182c416326
> # good: [d8bfeb4282b1c55342d2dd946eaf00f4f13785db] Merge branch 'for-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394.git
> git bisect good d8bfeb4282b1c55342d2dd946eaf00f4f13785db
> # bad: [f5315deb662e813be5fa93f2b67d46fe9fcd383c] Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git
> git bisect bad f5315deb662e813be5fa93f2b67d46fe9fcd383c
> # good: [4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0] ASoC: dt-bindings: amlogic,axg-sound-card: document clocks property
> git bisect good 4b1d9019b26fd654ebc2d0d2e100ed56ef1821f0
> # bad: [2ca98b409c36e91bb359a2997f4a7810e799bd62] Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git
> git bisect bad 2ca98b409c36e91bb359a2997f4a7810e799bd62
> # good: [d39b510a145a4766906cd49177695913d6e6bfd2] Add audio support for the MediaTek Genio 350-evk
> git bisect good d39b510a145a4766906cd49177695913d6e6bfd2
> # good: [43fbb2c702663d7af844ee952aec224a0e059e26] ASoC: loongson: Simplify code formatting
> git bisect good 43fbb2c702663d7af844ee952aec224a0e059e26
> # good: [0b0aa67baa8904e3c1e13be48a2ca125f59ead3d] ASoC: amd: acp: remove MODULE_ALIAS for sof based generic machine driver
> git bisect good 0b0aa67baa8904e3c1e13be48a2ca125f59ead3d
> # good: [8905d39085c60a13d47bd07d2766bfdde933cc8d] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git
> git bisect good 8905d39085c60a13d47bd07d2766bfdde933cc8d
> # good: [907fa79d787f6f762c0afb67b8b02be8ed1f7bd2] MAINTAINERS: scale modules with more reviewers
> git bisect good 907fa79d787f6f762c0afb67b8b02be8ed1f7bd2
> # bad: [e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7] module: abort module loading when sysfs setup suffer errors
> git bisect bad e1d90ff7bc4b93c0b6c4821bef71b51ce145d7a7
> # bad: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
> git bisect bad 7125cb974977aa80959817548b5221314fe46bc0
> # first bad commit: [7125cb974977aa80959817548b5221314fe46bc0] params: Annotate struct module_param_attrs with __counted_by()
Thanks for reporting this.
Changing
memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
to
memset(mk->mp->attrs + mk->mp->num - 1, 0, sizeof(mk->mp->attrs[0]));
fixes the false-positive warning
memset: detected buffer overflow: 32 byte write of buffer size 0
even though the pointers have the same value. Does anyone know why?
Thanks,
Thorsten
On Sat, Sep 14, 2024 at 01:32:19AM +0200, Thorsten Blum wrote: > Thanks for reporting this. > > Changing > > memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0])); > > to > > memset(mk->mp->attrs + mk->mp->num - 1, 0, sizeof(mk->mp->attrs[0])); > > fixes the false-positive warning > > memset: detected buffer overflow: 32 byte write of buffer size 0 > > even though the pointers have the same value. Does anyone know why? Might be a good question for Bill? The full context is available starting at: https://lore.kernel.org/all/20240913164630.GA4091534@thelio-3990X/ I wonder if the krealloc() has something to do with it? I should try GCC but I don't have a tip of tree copy handy at the moment and I am also rushing at the end of my day to pack for my travels to LPC :) Cheers, Nathan
On 14. Sep 2024, at 01:44, Nathan Chancellor <nathan@kernel.org> wrote: > On Sat, Sep 14, 2024 at 01:32:19AM +0200, Thorsten Blum wrote: >> Thanks for reporting this. >> >> Changing >> >> memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0])); >> >> to >> >> memset(mk->mp->attrs + mk->mp->num - 1, 0, sizeof(mk->mp->attrs[0])); >> >> fixes the false-positive warning >> >> memset: detected buffer overflow: 32 byte write of buffer size 0 >> >> even though the pointers have the same value. Does anyone know why? > > Might be a good question for Bill? The full context is available > starting at: > > https://lore.kernel.org/all/20240913164630.GA4091534@thelio-3990X/ > > I wonder if the krealloc() has something to do with it? I should try GCC > but I don't have a tip of tree copy handy at the moment and I am also > rushing at the end of my day to pack for my travels to LPC :) I think the problem is with __builtin_dynamic_object_size(). memset(p,,) calls __struct_size(p), which calls __builtin_dynamic_object_size(p, 0) and this behaves weirdly: __builtin_dynamic_object_size(&mk->mp->attrs[mk->mp->num - 1], 0); evaluates to 0, but __builtin_dynamic_object_size(mk->mp->attrs + mk->mp->num - 1, 0); evaluates to 4294967295. Both values are wrong, but the latter doesn't trigger the false-positive warning.
On Fri, Sep 13, 2024 at 5:23 PM Thorsten Blum <thorsten.blum@toblux.com> wrote: > > On 14. Sep 2024, at 01:44, Nathan Chancellor <nathan@kernel.org> wrote: > > On Sat, Sep 14, 2024 at 01:32:19AM +0200, Thorsten Blum wrote: > >> Thanks for reporting this. > >> > >> Changing > >> > >> memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0])); > >> > >> to > >> > >> memset(mk->mp->attrs + mk->mp->num - 1, 0, sizeof(mk->mp->attrs[0])); > >> > >> fixes the false-positive warning > >> > >> memset: detected buffer overflow: 32 byte write of buffer size 0 > >> > >> even though the pointers have the same value. Does anyone know why? > > > > Might be a good question for Bill? The full context is available > > starting at: > > > > https://lore.kernel.org/all/20240913164630.GA4091534@thelio-3990X/ > > > > I wonder if the krealloc() has something to do with it? I should try GCC > > but I don't have a tip of tree copy handy at the moment and I am also > > rushing at the end of my day to pack for my travels to LPC :) > > I think the problem is with __builtin_dynamic_object_size(). > > memset(p,,) calls __struct_size(p), which calls > __builtin_dynamic_object_size(p, 0) and this behaves weirdly: > > __builtin_dynamic_object_size(&mk->mp->attrs[mk->mp->num - 1], 0); > > evaluates to 0, but > > __builtin_dynamic_object_size(mk->mp->attrs + mk->mp->num - 1, 0); > > evaluates to 4294967295. > > Both values are wrong, but the latter doesn't trigger the > false-positive warning. The 4294967295 simply means "I don't know." There's probably a bug in the size calculation. I'll look into it. -bw
On Mon, Sep 16, 2024 at 02:45:47AM -0700, Bill Wendling wrote:
> The 4294967295 simply means "I don't know." There's probably a bug in
> the size calculation. I'll look into it.
I was able to build a minimized PoC, if that's helpful:
https://godbolt.org/z/qohGd5xh1
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
struct variable {
int a;
int b;
int length;
short array[] __attribute__((counted_by(length)));
};
struct bucket {
int a;
struct variable *growable;
int b;
};
int main(int argc, char *argv[])
{
struct bucket *p;
struct variable *v;
p = malloc(sizeof(*p));
v = malloc(sizeof(*p->growable) + sizeof(*p->growable->array) * 32);
v->length = 32;
printf("%zu\n", __builtin_dynamic_object_size(v->array, 1));
p->growable = v;
printf("%zu\n", __builtin_dynamic_object_size(p->growable->array, 1));
return 0;
}
GCC shows 64 64, but Clang shows 64 0.
--
Kees Cook
On Fri, Sep 13, 2024 at 09:46:30AM -0700, Nathan Chancellor wrote: > On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote: > > Add the __counted_by compiler attribute to the flexible array member > > attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > > CONFIG_FORTIFY_SOURCE. > > > > Increment num before adding a new param_attribute to the attrs array and > > adjust the array index accordingly. Increment num immediately after the > > first reallocation such that the reallocation for the NULL terminator > > only needs to add 1 (instead of 2) to mk->mp->num. > > > > Use struct_size() instead of manually calculating the size for the > > reallocation. > > > > Use krealloc_array() for the additional NULL terminator. > > /* Fix up all the pointers, since krealloc can move us */ > > for (i = 0; i < mk->mp->num; i++) Shouldn't this for loop and followed by assignment also be -1:ed? -- With Best Regards, Andy Shevchenko
On 13. Sep 2024, at 20:40, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > On Fri, Sep 13, 2024 at 09:46:30AM -0700, Nathan Chancellor wrote: >> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote: >>> Add the __counted_by compiler attribute to the flexible array member >>> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and >>> CONFIG_FORTIFY_SOURCE. >>> >>> Increment num before adding a new param_attribute to the attrs array and >>> adjust the array index accordingly. Increment num immediately after the >>> first reallocation such that the reallocation for the NULL terminator >>> only needs to add 1 (instead of 2) to mk->mp->num. >>> >>> Use struct_size() instead of manually calculating the size for the >>> reallocation. >>> >>> Use krealloc_array() for the additional NULL terminator. > >>> /* Fix up all the pointers, since krealloc can move us */ >>> for (i = 0; i < mk->mp->num; i++) > > Shouldn't this for loop and followed by assignment also be -1:ed? That should be fine as mk->mp->num was already incremented before the for-loop.
On Fri, Sep 13, 2024 at 09:03:06PM +0200, Thorsten Blum wrote: > On 13. Sep 2024, at 20:40, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Fri, Sep 13, 2024 at 09:46:30AM -0700, Nathan Chancellor wrote: > >> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote: > >>> Add the __counted_by compiler attribute to the flexible array member > >>> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > >>> CONFIG_FORTIFY_SOURCE. > >>> > >>> Increment num before adding a new param_attribute to the attrs array and > >>> adjust the array index accordingly. Increment num immediately after the > >>> first reallocation such that the reallocation for the NULL terminator > >>> only needs to add 1 (instead of 2) to mk->mp->num. > >>> > >>> Use struct_size() instead of manually calculating the size for the > >>> reallocation. > >>> > >>> Use krealloc_array() for the additional NULL terminator. > > > >>> /* Fix up all the pointers, since krealloc can move us */ > >>> for (i = 0; i < mk->mp->num; i++) > > > > Shouldn't this for loop and followed by assignment also be -1:ed? > > That should be fine as mk->mp->num was already incremented before the > for-loop. Exactly my point. This is behavioural change AFAICS as the original code used the old (-1:ed) value, no? -- With Best Regards, Andy Shevchenko
On Fri, Sep 13, 2024 at 10:09:25PM +0300, Andy Shevchenko wrote: > On Fri, Sep 13, 2024 at 09:03:06PM +0200, Thorsten Blum wrote: > > On 13. Sep 2024, at 20:40, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > > On Fri, Sep 13, 2024 at 09:46:30AM -0700, Nathan Chancellor wrote: > > >> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote: > > >>> Add the __counted_by compiler attribute to the flexible array member > > >>> attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > > >>> CONFIG_FORTIFY_SOURCE. > > >>> > > >>> Increment num before adding a new param_attribute to the attrs array and > > >>> adjust the array index accordingly. Increment num immediately after the > > >>> first reallocation such that the reallocation for the NULL terminator > > >>> only needs to add 1 (instead of 2) to mk->mp->num. > > >>> > > >>> Use struct_size() instead of manually calculating the size for the > > >>> reallocation. > > >>> > > >>> Use krealloc_array() for the additional NULL terminator. > > > > > >>> /* Fix up all the pointers, since krealloc can move us */ > > >>> for (i = 0; i < mk->mp->num; i++) > > > > > > Shouldn't this for loop and followed by assignment also be -1:ed? > > > > That should be fine as mk->mp->num was already incremented before the > > for-loop. > > Exactly my point. This is behavioural change AFAICS as the original code used > the old (-1:ed) value, no? Ah, I see now. It was in the original code, but closer to that loop... -- With Best Regards, Andy Shevchenko
On Fri, Sep 13, 2024 at 09:46:30AM -0700, Nathan Chancellor wrote:
> Hi Thorsten,
>
> On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote:
> > Add the __counted_by compiler attribute to the flexible array member
> > attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> > CONFIG_FORTIFY_SOURCE.
> >
> > Increment num before adding a new param_attribute to the attrs array and
> > adjust the array index accordingly. Increment num immediately after the
> > first reallocation such that the reallocation for the NULL terminator
> > only needs to add 1 (instead of 2) to mk->mp->num.
> >
> > Use struct_size() instead of manually calculating the size for the
> > reallocation.
> >
> > Use krealloc_array() for the additional NULL terminator.
> >
> > Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
> > ---
> > Changes in v2:
> > - Use krealloc_array() as suggested by Andy Shevchenko
> > - Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/
> > ---
> > kernel/params.c | 29 +++++++++++++----------------
> > 1 file changed, 13 insertions(+), 16 deletions(-)
> >
> > diff --git a/kernel/params.c b/kernel/params.c
> > index 2e447f8ae183..5f6643676697 100644
> > --- a/kernel/params.c
> > +++ b/kernel/params.c
> > @@ -551,7 +551,7 @@ struct module_param_attrs
> > {
> > unsigned int num;
> > struct attribute_group grp;
> > - struct param_attribute attrs[];
> > + struct param_attribute attrs[] __counted_by(num);
> > };
> >
> > #ifdef CONFIG_SYSFS
> > @@ -651,35 +651,32 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
> > }
> >
> > /* Enlarge allocations. */
> > - new_mp = krealloc(mk->mp,
> > - sizeof(*mk->mp) +
> > - sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
> > + new_mp = krealloc(mk->mp, struct_size(mk->mp, attrs, mk->mp->num + 1),
> > GFP_KERNEL);
> > if (!new_mp)
> > return -ENOMEM;
> > mk->mp = new_mp;
> > + mk->mp->num++;
> >
> > /* Extra pointer for NULL terminator */
> > - new_attrs = krealloc(mk->mp->grp.attrs,
> > - sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
> > - GFP_KERNEL);
> > + new_attrs = krealloc_array(mk->mp->grp.attrs, mk->mp->num + 1,
> > + sizeof(mk->mp->grp.attrs[0]), GFP_KERNEL);
> > if (!new_attrs)
> > return -ENOMEM;
> > mk->mp->grp.attrs = new_attrs;
> >
> > /* Tack new one on the end. */
> > - memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
> > - sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
> > - mk->mp->attrs[mk->mp->num].param = kp;
> > - mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
> > + memset(&mk->mp->attrs[mk->mp->num - 1], 0, sizeof(mk->mp->attrs[0]));
> > + sysfs_attr_init(&mk->mp->attrs[mk->mp->num - 1].mattr.attr);
> > + mk->mp->attrs[mk->mp->num - 1].param = kp;
> > + mk->mp->attrs[mk->mp->num - 1].mattr.show = param_attr_show;
> > /* Do not allow runtime DAC changes to make param writable. */
> > if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
> > - mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
> > + mk->mp->attrs[mk->mp->num - 1].mattr.store = param_attr_store;
> > else
> > - mk->mp->attrs[mk->mp->num].mattr.store = NULL;
> > - mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
> > - mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
> > - mk->mp->num++;
> > + mk->mp->attrs[mk->mp->num - 1].mattr.store = NULL;
> > + mk->mp->attrs[mk->mp->num - 1].mattr.attr.name = (char *)name;
> > + mk->mp->attrs[mk->mp->num - 1].mattr.attr.mode = kp->perm;
> >
> > /* Fix up all the pointers, since krealloc can move us */
> > for (i = 0; i < mk->mp->num; i++)
> > --
> > 2.46.0
> >
>
> I just bisected this change to a fortify failure that I see with a
> couple different ARM configurations when built with a version of clang
> that supports __counted_by(). I can reproduce this with:
>
> $ curl -LSso .config https://gist.github.com/nathanchance/6df4bd2ab4c4418020b3ed5417ef4f80/raw/758abf666dfe8c76e0f16735f336849ea47ef791/.config
>
> $ make -skj"$(nproc)" ARCH=arm LLVM=1 olddefconfig zImage
>
> $ curl -LSs https://github.com/ClangBuiltLinux/boot-utils/releases/download/20230707-182910/arm-rootfs.cpio.zst | zstd -d >rootfs.cpio
>
> $ qemu-system-arm \
> -display none \
> -nodefaults \
> -no-reboot \
> -machine virt \
> -append 'console=ttyAMA0 earlycon' \
> -kernel arch/arm/boot/zImage \
> -initrd rootfs.cpio \
> -m 512m \
> -serial mon:stdio
> [ 0.000000] Booting Linux on physical CPU 0x0
> [ 0.000000] Linux version 6.11.0-rc4+ (nathan@thelio-3990X) (ClangBuiltLinux clang version 19.1.0-rc4 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87), ClangBuiltLinux LLD 19.1.0 (https://github.com/llvm/llvm-project.git 0c641568515a797473394694f05937e1f1913d87)) #1 SMP Fri Sep 13 09:36:38 MST 2024
> ...
Thanks, I've dropped this patch from modules-next for now.
Luis
On Mon, Sep 09, 2024 at 06:27:26PM +0200, Thorsten Blum wrote: > Add the __counted_by compiler attribute to the flexible array member > attrs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and > CONFIG_FORTIFY_SOURCE. > > Increment num before adding a new param_attribute to the attrs array and > adjust the array index accordingly. Increment num immediately after the > first reallocation such that the reallocation for the NULL terminator > only needs to add 1 (instead of 2) to mk->mp->num. > > Use struct_size() instead of manually calculating the size for the > reallocation. > > Use krealloc_array() for the additional NULL terminator. > > Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> > --- > Changes in v2: > - Use krealloc_array() as suggested by Andy Shevchenko > - Link to v1: https://lore.kernel.org/linux-kernel/20240823123300.37574-1-thorsten.blum@toblux.com/ Applied and pushed to modules-next, thanks! Luis
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