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[PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE

Marco Elver posted 1 patch 4 years, 5 months ago 
lib/test_kasan.c | 5 +++++
1 file changed, 5 insertions(+)
[PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Posted by Marco Elver 4 years, 5 months ago 
With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
dynamic checks using __builtin_object_size(ptr), which when failed will
panic the kernel.

Because the KASAN test deliberately performs out-of-bounds operations,
the kernel panics with FORITY_SOURCE, for example:

 | kernel BUG at lib/string_helpers.c:910!
 | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
 | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G    B             5.16.0-rc3+ #3
 | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
 | RIP: 0010:fortify_panic+0x19/0x1b
 | ...
 | Call Trace:
 |  <TASK>
 |  kmalloc_oob_in_memset.cold+0x16/0x16
 |  ...

Fix it by also hiding `ptr` from the optimizer, which will ensure that
__builtin_object_size() does not return a valid size, preventing
fortified string functions from panicking.

Reported-by: Nico Pache <npache@redhat.com>
Signed-off-by: Marco Elver <elver@google.com>
---
 lib/test_kasan.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 847cdbefab46..26a5c9007653 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -492,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
 	KUNIT_EXPECT_KASAN_FAIL(test,
 				memset(ptr, 0, size + KASAN_GRANULE_SIZE));
@@ -515,6 +516,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
 	memset((char *)ptr, 0, 64);
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(invalid_size);
 	KUNIT_EXPECT_KASAN_FAIL(test,
 		memmove((char *)ptr, (char *)ptr + 4, invalid_size));
@@ -531,6 +533,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
 	memset((char *)ptr, 0, 64);
+	OPTIMIZER_HIDE_VAR(ptr);
 	KUNIT_EXPECT_KASAN_FAIL(test,
 		memmove((char *)ptr, (char *)ptr + 4, invalid_size));
 	kfree(ptr);
@@ -893,6 +896,7 @@ static void kasan_memchr(struct kunit *test)
 	ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
 	KUNIT_EXPECT_KASAN_FAIL(test,
 		kasan_ptr_result = memchr(ptr, '1', size + 1));
@@ -919,6 +923,7 @@ static void kasan_memcmp(struct kunit *test)
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 	memset(arr, 0, sizeof(arr));
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
 	KUNIT_EXPECT_KASAN_FAIL(test,
 		kasan_int_result = memcmp(ptr, arr, size+1));
-- 
2.35.0.rc0.227.g00780c9af4-goog
Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Posted by Andrey Konovalov 4 years, 5 months ago 
 -On Mon, Jan 24, 2022 at 5:07 PM Marco Elver <elver@google.com> wrote:
>
> With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
> dynamic checks using __builtin_object_size(ptr), which when failed will
> panic the kernel.
>
> Because the KASAN test deliberately performs out-of-bounds operations,
> the kernel panics with FORITY_SOURCE, for example:

Nit: FORITY_SOURCE -> FORTIFY_SOURCE

>
>  | kernel BUG at lib/string_helpers.c:910!
>  | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
>  | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G    B             5.16.0-rc3+ #3
>  | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
>  | RIP: 0010:fortify_panic+0x19/0x1b
>  | ...
>  | Call Trace:
>  |  <TASK>
>  |  kmalloc_oob_in_memset.cold+0x16/0x16
>  |  ...
>
> Fix it by also hiding `ptr` from the optimizer, which will ensure that
> __builtin_object_size() does not return a valid size, preventing
> fortified string functions from panicking.
>
> Reported-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Marco Elver <elver@google.com>
> ---
>  lib/test_kasan.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 847cdbefab46..26a5c9007653 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -492,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
>         ptr = kmalloc(size, GFP_KERNEL);
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> +       OPTIMIZER_HIDE_VAR(ptr);
>         OPTIMIZER_HIDE_VAR(size);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                                 memset(ptr, 0, size + KASAN_GRANULE_SIZE));
> @@ -515,6 +516,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
>         memset((char *)ptr, 0, 64);
> +       OPTIMIZER_HIDE_VAR(ptr);
>         OPTIMIZER_HIDE_VAR(invalid_size);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                 memmove((char *)ptr, (char *)ptr + 4, invalid_size));
> @@ -531,6 +533,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
>         memset((char *)ptr, 0, 64);
> +       OPTIMIZER_HIDE_VAR(ptr);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                 memmove((char *)ptr, (char *)ptr + 4, invalid_size));
>         kfree(ptr);
> @@ -893,6 +896,7 @@ static void kasan_memchr(struct kunit *test)
>         ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> +       OPTIMIZER_HIDE_VAR(ptr);
>         OPTIMIZER_HIDE_VAR(size);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                 kasan_ptr_result = memchr(ptr, '1', size + 1));
> @@ -919,6 +923,7 @@ static void kasan_memcmp(struct kunit *test)
>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>         memset(arr, 0, sizeof(arr));
>
> +       OPTIMIZER_HIDE_VAR(ptr);
>         OPTIMIZER_HIDE_VAR(size);
>         KUNIT_EXPECT_KASAN_FAIL(test,
>                 kasan_int_result = memcmp(ptr, arr, size+1));
> --
> 2.35.0.rc0.227.g00780c9af4-goog
>

Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Posted by Marco Elver 4 years, 5 months ago 
On Mon, 24 Jan 2022 at 18:54, Andrey Konovalov <andreyknvl@gmail.com> wrote:
>
>  -On Mon, Jan 24, 2022 at 5:07 PM Marco Elver <elver@google.com> wrote:
> >
> > With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
> > dynamic checks using __builtin_object_size(ptr), which when failed will
> > panic the kernel.
> >
> > Because the KASAN test deliberately performs out-of-bounds operations,
> > the kernel panics with FORITY_SOURCE, for example:
>
> Nit: FORITY_SOURCE -> FORTIFY_SOURCE

How did that happen?! My hands need some better synchronization...

I'll refrain sending a v2, assuming Andrew can fix up this spelling
mistake upon applying.

[...]
>
> Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>

Thanks!
Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Posted by Nico Pache 4 years, 5 months ago 

On 1/24/22 11:07, Marco Elver wrote:
> With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
> dynamic checks using __builtin_object_size(ptr), which when failed will
> panic the kernel.
> 
> Because the KASAN test deliberately performs out-of-bounds operations,
> the kernel panics with FORITY_SOURCE, for example:
> 
>  | kernel BUG at lib/string_helpers.c:910!
>  | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
>  | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G    B             5.16.0-rc3+ #3
>  | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
>  | RIP: 0010:fortify_panic+0x19/0x1b
>  | ...
>  | Call Trace:
>  |  <TASK>
>  |  kmalloc_oob_in_memset.cold+0x16/0x16
>  |  ...
> 
> Fix it by also hiding `ptr` from the optimizer, which will ensure that
> __builtin_object_size() does not return a valid size, preventing
> fortified string functions from panicking.
> 
> Reported-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Marco Elver <elver@google.com>

Looks good! Thanks for posting this Marco :)

Reviewed-by: Nico Pache <npache@redhat.com>

> ---
>  lib/test_kasan.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 847cdbefab46..26a5c9007653 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -492,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
>  	ptr = kmalloc(size, GFP_KERNEL);
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  
> +	OPTIMIZER_HIDE_VAR(ptr);
>  	OPTIMIZER_HIDE_VAR(size);
>  	KUNIT_EXPECT_KASAN_FAIL(test,
>  				memset(ptr, 0, size + KASAN_GRANULE_SIZE));
> @@ -515,6 +516,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  
>  	memset((char *)ptr, 0, 64);
> +	OPTIMIZER_HIDE_VAR(ptr);
>  	OPTIMIZER_HIDE_VAR(invalid_size);
>  	KUNIT_EXPECT_KASAN_FAIL(test,
>  		memmove((char *)ptr, (char *)ptr + 4, invalid_size));
> @@ -531,6 +533,7 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  
>  	memset((char *)ptr, 0, 64);
> +	OPTIMIZER_HIDE_VAR(ptr);
>  	KUNIT_EXPECT_KASAN_FAIL(test,
>  		memmove((char *)ptr, (char *)ptr + 4, invalid_size));
>  	kfree(ptr);
> @@ -893,6 +896,7 @@ static void kasan_memchr(struct kunit *test)
>  	ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  
> +	OPTIMIZER_HIDE_VAR(ptr);
>  	OPTIMIZER_HIDE_VAR(size);
>  	KUNIT_EXPECT_KASAN_FAIL(test,
>  		kasan_ptr_result = memchr(ptr, '1', size + 1));
> @@ -919,6 +923,7 @@ static void kasan_memcmp(struct kunit *test)
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  	memset(arr, 0, sizeof(arr));
>  
> +	OPTIMIZER_HIDE_VAR(ptr);
>  	OPTIMIZER_HIDE_VAR(size);
>  	KUNIT_EXPECT_KASAN_FAIL(test,
>  		kasan_int_result = memcmp(ptr, arr, size+1));
>
Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE
Posted by Kees Cook 4 years, 5 months ago 
On Mon, Jan 24, 2022 at 05:07:44PM +0100, Marco Elver wrote:
> With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform
> dynamic checks using __builtin_object_size(ptr), which when failed will
> panic the kernel.
> 
> Because the KASAN test deliberately performs out-of-bounds operations,
> the kernel panics with FORITY_SOURCE, for example:
> 
>  | kernel BUG at lib/string_helpers.c:910!
>  | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
>  | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G    B             5.16.0-rc3+ #3
>  | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
>  | RIP: 0010:fortify_panic+0x19/0x1b
>  | ...
>  | Call Trace:
>  |  <TASK>
>  |  kmalloc_oob_in_memset.cold+0x16/0x16
>  |  ...
> 
> Fix it by also hiding `ptr` from the optimizer, which will ensure that
> __builtin_object_size() does not return a valid size, preventing
> fortified string functions from panicking.
> 
> Reported-by: Nico Pache <npache@redhat.com>
> Signed-off-by: Marco Elver <elver@google.com>

Yup, more good fixes. Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Patchew 2.1-devel-ea86937

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