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[PATCH RFC v3 4/4] module: refactor ro_after_init failure path

Daniel Gomez via B4 Relay posted 4 patches 2 weeks, 1 day ago
[PATCH RFC v3 4/4] module: refactor ro_after_init failure path
Posted by Daniel Gomez via B4 Relay 2 weeks, 1 day ago 
From: Daniel Gomez <da.gomez@samsung.com>

When ro_after_init fails, we need to unload the module.

Rename the goto tag to fail_ro_after_init to make it more clear and try
to check for dependencies, stop the module and call the exit function.
This allows to unload the module if ro_after_init fails.

This fixes the following error in block loop device driver when forcing
ro_after_init error path:

Nov 06 11:36:25 debian kernel: loop: module loaded
Nov 06 11:36:25 debian kernel: BUG: unable to handle page fault for
address: ffffffffa0006320
Nov 06 11:36:25 debian kernel: #PF: supervisor read access in kernel mode
Nov 06 11:36:25 debian kernel: #PF: error_code(0x0000) - not-present page
Nov 06 11:36:25 debian kernel: PGD 1e3f067 P4D 1e3f067 PUD 1e40063 PMD
10e7d4067 PTE 0
Nov 06 11:36:25 debian kernel: Oops: Oops: 0000 [#1]
Nov 06 11:36:25 debian kernel: CPU: 0 UID: 0 PID: 428 Comm:
(udev-worker) Not tainted 6.12.0-rc6-g4ade030a2d1b #155
Nov 06 11:36:25 debian kernel: Hardware name: QEMU Standard PC (Q35 +
ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Nov 06 11:36:25 debian kernel: RIP: 0010:bdev_open+0x83/0x290
Nov 06 11:36:25 debian kernel: Code: bb 48 01 00 00 48 89 3c 24 e8 79 24
38 00 48 8b 43 40 41 bd fa ff ff ff 48 83 b8 40 03 00 00 00 0f 84 b3 01
00 00 48 8b 43 48 <48> 8b 78 78 e8 d4 c9 c8 ff 84 c0 0f 84 9e 01 00 00
80 3d 45 ad ad
Nov 06 11:36:25 debian kernel: RSP: 0018:ffff8881054dbc58 EFLAGS:
00010286
Nov 06 11:36:25 debian kernel: RAX: ffffffffa00062a8 RBX:
ffff8881054a6800 RCX: ffff8881075becc0
Nov 06 11:36:25 debian kernel: RDX: 0000000000000000 RSI:
0000000000000009 RDI: ffff8881054a6948
Nov 06 11:36:25 debian kernel: RBP: 0000000000000009 R08:
ffff88810e7aa9c0 R09: 0000000000000000
Nov 06 11:36:25 debian kernel: R10: ffff88810e5ab0c0 R11:
ffff88810e796190 R12: ffff88810094e980
Nov 06 11:36:25 debian kernel: R13: 00000000fffffffa R14:
0000000000000000 R15: 0000000000000000
Nov 06 11:36:25 debian kernel: FS:  00007fd2ff110900(0000)
GS:ffffffff81e47000(0000) knlGS:0000000000000000
Nov 06 11:36:25 debian kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
0000000080050033
Nov 06 11:36:25 debian kernel: CR2: ffffffffa0006320 CR3:
000000010e7ed004 CR4: 00000000003706b0
Nov 06 11:36:25 debian kernel: Call Trace:
Nov 06 11:36:25 debian kernel:  <TASK>
Nov 06 11:36:25 debian kernel:  ? __die_body+0x16/0x60
Nov 06 11:36:25 debian kernel:  ? page_fault_oops+0x22a/0x310
Nov 06 11:36:25 debian kernel:  ? exc_page_fault+0x99/0xa0
Nov 06 11:36:25 debian kernel:  ? asm_exc_page_fault+0x22/0x30
Nov 06 11:36:25 debian kernel:  ? bdev_open+0x83/0x290
Nov 06 11:36:25 debian kernel:  ? bdev_open+0x67/0x290
Nov 06 11:36:25 debian kernel:  ? iput+0x37/0x150
Nov 06 11:36:25 debian kernel:  ? blkdev_open+0xab/0xd0
Nov 06 11:36:25 debian kernel:  ? blkdev_mmap+0x60/0x60
Nov 06 11:36:25 debian kernel:  ? do_dentry_open+0x25d/0x3b0
Nov 06 11:36:25 debian kernel:  ? vfs_open+0x1e/0xc0
Nov 06 11:36:25 debian kernel:  ? path_openat+0x9cf/0xbb0
Nov 06 11:36:25 debian kernel:  ? do_filp_open+0x7f/0xd0
Nov 06 11:36:25 debian kernel:  ? do_sys_openat2+0x67/0xb0
Nov 06 11:36:25 debian kernel:  ? do_sys_open+0x4b/0x50
Nov 06 11:36:25 debian kernel:  ? do_syscall_64+0x3d/0xb0
Nov 06 11:36:25 debian kernel:  ? entry_SYSCALL_64_after_hwframe+0x4b/0x53
Nov 06 11:36:25 debian kernel:  </TASK>
Nov 06 11:36:25 debian kernel: Modules linked in:
Nov 06 11:36:25 debian kernel: CR2: ffffffffa0006320
Nov 06 11:36:25 debian kernel: ---[ end trace 0000000000000000 ]---

./scripts/faddr2line --list vmlinux bdev_open+0x83/0x290
bdev_open+0x83/0x290:

bdev_open at block/bdev.c:908
 903
 904            mutex_lock(&disk->open_mutex);
 905            ret = -ENXIO;
 906            if (!disk_live(disk))
 907                    goto abort_claiming;
>908<           if (!try_module_get(disk->fops->owner))
 909                    goto abort_claiming;
 910            ret = -EBUSY;
 911            if (!bdev_may_open(bdev, mode))
 912                    goto put_module;
 913            if (bdev_is_partition(bdev))

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Closes: https://lore.kernel.org/all/20230915082126.4187913-1-ruanjinjie@huawei.com/
Fixes: d1909c022173 ("module: Don't ignore errors from set_memory_XX()").
Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
---
 kernel/module/main.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 2b45a6efa0a9..c23521ae8bda 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2880,7 +2880,7 @@ module_param(async_probe, bool, 0644);
  */
 static noinline int do_init_module(struct module *mod)
 {
-	int ret = 0;
+	int ret = 0, forced = 0;
 	struct mod_initfree *freeinit;
 #if defined(CONFIG_MODULE_STATS)
 	unsigned int text_size = 0, total_size = 0;
@@ -2948,7 +2948,7 @@ static noinline int do_init_module(struct module *mod)
 #endif
 	ret = module_enable_rodata_ro(mod, true);
 	if (ret)
-		goto fail_mutex_unlock;
+		goto fail_ro_after_init;
 	/* Drop initial reference. */
 	module_put(mod);
 	mod_tree_remove_init(mod);
@@ -2989,8 +2989,12 @@ static noinline int do_init_module(struct module *mod)
 
 	return 0;
 
-fail_mutex_unlock:
+fail_ro_after_init:
+	list_empty(&mod->source_list);
+	try_stop_module(mod, 0, &forced);
 	mutex_unlock(&module_mutex);
+	if (mod->exit != NULL)
+		mod->exit();
 fail_free_freeinit:
 	kfree(freeinit);
 fail:

-- 
2.39.2
Re: [PATCH RFC v3 4/4] module: refactor ro_after_init failure path
Posted by Christophe Leroy 2 weeks ago 

Le 08/11/2024 à 17:12, Daniel Gomez via B4 Relay a écrit :
> [Vous ne recevez pas souvent de courriers de devnull+da.gomez.samsung.com@kernel.org. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> 
> From: Daniel Gomez <da.gomez@samsung.com>
> 
> When ro_after_init fails, we need to unload the module.
> 
> Rename the goto tag to fail_ro_after_init to make it more clear and try
> to check for dependencies, stop the module and call the exit function.
> This allows to unload the module if ro_after_init fails.

Doesn't build:

   CC      kernel/module/main.o
kernel/module/main.c: In function 'do_init_module':
kernel/module/main.c:2626:19: error: 'struct module' has no member named 
'source_list'; did you mean 'bug_list'?
   list_empty(&mod->source_list);
                    ^~~~~~~~~~~
                    bug_list
kernel/module/main.c:2627:2: error: implicit declaration of function 
'try_stop_module'; did you mean 'do_init_module'? 
[-Werror=implicit-function-declaration]
   try_stop_module(mod, 0, &forced);
   ^~~~~~~~~~~~~~~
   do_init_module
kernel/module/main.c:2629:11: error: 'struct module' has no member named 
'exit'; did you mean 'init'?
   if (mod->exit != NULL)
            ^~~~
            init
kernel/module/main.c:2630:8: error: 'struct module' has no member named 
'exit'; did you mean 'init'?
    mod->exit();
         ^~~~
         init



Christophe
Re: [PATCH RFC v3 4/4] module: refactor ro_after_init failure path
Posted by Luis Chamberlain 2 weeks, 1 day ago 
On Fri, Nov 08, 2024 at 05:12:16PM +0100, Daniel Gomez via B4 Relay wrote:
> From: Daniel Gomez <da.gomez@samsung.com>
> 
> When ro_after_init fails, we need to unload the module.
> 
> Rename the goto tag to fail_ro_after_init to make it more clear and try
> to check for dependencies, stop the module and call the exit function.
> This allows to unload the module if ro_after_init fails.
> 
> This fixes the following error in block loop device driver when forcing
> ro_after_init error path:
> 
> Nov 06 11:36:25 debian kernel: loop: module loaded
> Nov 06 11:36:25 debian kernel: BUG: unable to handle page fault for
> address: ffffffffa0006320
> Nov 06 11:36:25 debian kernel: #PF: supervisor read access in kernel mode
> Nov 06 11:36:25 debian kernel: #PF: error_code(0x0000) - not-present page
> Nov 06 11:36:25 debian kernel: PGD 1e3f067 P4D 1e3f067 PUD 1e40063 PMD
> 10e7d4067 PTE 0
> Nov 06 11:36:25 debian kernel: Oops: Oops: 0000 [#1]
> Nov 06 11:36:25 debian kernel: CPU: 0 UID: 0 PID: 428 Comm:
> (udev-worker) Not tainted 6.12.0-rc6-g4ade030a2d1b #155
> Nov 06 11:36:25 debian kernel: Hardware name: QEMU Standard PC (Q35 +
> ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> Nov 06 11:36:25 debian kernel: RIP: 0010:bdev_open+0x83/0x290
> Nov 06 11:36:25 debian kernel: Code: bb 48 01 00 00 48 89 3c 24 e8 79 24
> 38 00 48 8b 43 40 41 bd fa ff ff ff 48 83 b8 40 03 00 00 00 0f 84 b3 01
> 00 00 48 8b 43 48 <48> 8b 78 78 e8 d4 c9 c8 ff 84 c0 0f 84 9e 01 00 00
> 80 3d 45 ad ad
> Nov 06 11:36:25 debian kernel: RSP: 0018:ffff8881054dbc58 EFLAGS:
> 00010286
> Nov 06 11:36:25 debian kernel: RAX: ffffffffa00062a8 RBX:
> ffff8881054a6800 RCX: ffff8881075becc0
> Nov 06 11:36:25 debian kernel: RDX: 0000000000000000 RSI:
> 0000000000000009 RDI: ffff8881054a6948
> Nov 06 11:36:25 debian kernel: RBP: 0000000000000009 R08:
> ffff88810e7aa9c0 R09: 0000000000000000
> Nov 06 11:36:25 debian kernel: R10: ffff88810e5ab0c0 R11:
> ffff88810e796190 R12: ffff88810094e980
> Nov 06 11:36:25 debian kernel: R13: 00000000fffffffa R14:
> 0000000000000000 R15: 0000000000000000
> Nov 06 11:36:25 debian kernel: FS:  00007fd2ff110900(0000)
> GS:ffffffff81e47000(0000) knlGS:0000000000000000
> Nov 06 11:36:25 debian kernel: CS:  0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033
> Nov 06 11:36:25 debian kernel: CR2: ffffffffa0006320 CR3:
> 000000010e7ed004 CR4: 00000000003706b0
> Nov 06 11:36:25 debian kernel: Call Trace:
> Nov 06 11:36:25 debian kernel:  <TASK>
> Nov 06 11:36:25 debian kernel:  ? __die_body+0x16/0x60
> Nov 06 11:36:25 debian kernel:  ? page_fault_oops+0x22a/0x310
> Nov 06 11:36:25 debian kernel:  ? exc_page_fault+0x99/0xa0
> Nov 06 11:36:25 debian kernel:  ? asm_exc_page_fault+0x22/0x30
> Nov 06 11:36:25 debian kernel:  ? bdev_open+0x83/0x290
> Nov 06 11:36:25 debian kernel:  ? bdev_open+0x67/0x290
> Nov 06 11:36:25 debian kernel:  ? iput+0x37/0x150
> Nov 06 11:36:25 debian kernel:  ? blkdev_open+0xab/0xd0
> Nov 06 11:36:25 debian kernel:  ? blkdev_mmap+0x60/0x60
> Nov 06 11:36:25 debian kernel:  ? do_dentry_open+0x25d/0x3b0
> Nov 06 11:36:25 debian kernel:  ? vfs_open+0x1e/0xc0
> Nov 06 11:36:25 debian kernel:  ? path_openat+0x9cf/0xbb0
> Nov 06 11:36:25 debian kernel:  ? do_filp_open+0x7f/0xd0
> Nov 06 11:36:25 debian kernel:  ? do_sys_openat2+0x67/0xb0
> Nov 06 11:36:25 debian kernel:  ? do_sys_open+0x4b/0x50
> Nov 06 11:36:25 debian kernel:  ? do_syscall_64+0x3d/0xb0
> Nov 06 11:36:25 debian kernel:  ? entry_SYSCALL_64_after_hwframe+0x4b/0x53
> Nov 06 11:36:25 debian kernel:  </TASK>
> Nov 06 11:36:25 debian kernel: Modules linked in:
> Nov 06 11:36:25 debian kernel: CR2: ffffffffa0006320
> Nov 06 11:36:25 debian kernel: ---[ end trace 0000000000000000 ]---
> 
> ./scripts/faddr2line --list vmlinux bdev_open+0x83/0x290
> bdev_open+0x83/0x290:
> 
> bdev_open at block/bdev.c:908
>  903
>  904            mutex_lock(&disk->open_mutex);
>  905            ret = -ENXIO;
>  906            if (!disk_live(disk))
>  907                    goto abort_claiming;
> >908<           if (!try_module_get(disk->fops->owner))
>  909                    goto abort_claiming;
>  910            ret = -EBUSY;
>  911            if (!bdev_may_open(bdev, mode))
>  912                    goto put_module;
>  913            if (bdev_is_partition(bdev))
> 
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Closes: https://lore.kernel.org/all/20230915082126.4187913-1-ruanjinjie@huawei.com/
> Fixes: d1909c022173 ("module: Don't ignore errors from set_memory_XX()").
> Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
> ---
>  kernel/module/main.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 2b45a6efa0a9..c23521ae8bda 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2880,7 +2880,7 @@ module_param(async_probe, bool, 0644);
>   */
>  static noinline int do_init_module(struct module *mod)
>  {
> -	int ret = 0;
> +	int ret = 0, forced = 0;
>  	struct mod_initfree *freeinit;
>  #if defined(CONFIG_MODULE_STATS)
>  	unsigned int text_size = 0, total_size = 0;
> @@ -2948,7 +2948,7 @@ static noinline int do_init_module(struct module *mod)
>  #endif

It is not clear here but note that do_init_module() happens
before the module is live and so any try_module_get() in the
do_init_module() path should fail.

>  	ret = module_enable_rodata_ro(mod, true);

But here do_init_module() should be have completed and the module is live.
So a open() on a block device *can* race after init, at which point
if open uses do_init_module() then it snatches a ref.

>  	if (ret)
> -		goto fail_mutex_unlock;
> +		goto fail_ro_after_init;
>  	/* Drop initial reference. */
>  	module_put(mod);
>  	mod_tree_remove_init(mod);
> @@ -2989,8 +2989,12 @@ static noinline int do_init_module(struct module *mod)
>  
>  	return 0;
>  
> -fail_mutex_unlock:
> +fail_ro_after_init:
> +	list_empty(&mod->source_list);
> +	try_stop_module(mod, 0, &forced);

Which is why try_stop_module() can fail here. But we don't want to fail.

This is a chicken and egg, since we are already live we can't stop
the world created from undernath us from not using try_module_get(),
as its the right thing to do.

The above sledge hammer can fail then and we don't want that.

>  	mutex_unlock(&module_mutex);
> +	if (mod->exit != NULL)
> +		mod->exit();
>  fail_free_freeinit:
>  	kfree(freeinit);
>  fail:

So I'd prefer a soolution which is clearer, and doesn't have to deal
with all these complexities somehow.

 Luis

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