* [PATCH] mm/kmemleak: silence KCSAN splats in checksum
@ 2020-03-17 18:27 Qian Cai
2020-03-17 18:41 ` Marco Elver
2020-03-18 8:51 ` Catalin Marinas
0 siblings, 2 replies; 3+ messages in thread
From: Qian Cai @ 2020-03-17 18:27 UTC (permalink / raw)
To: akpm; +Cc: elver, catalin.marinas, linux-mm, linux-kernel, Qian Cai
Even if KCSAN is disabled for kmemleak, update_checksum() could still
call crc32() (which is outside of kmemleak.c) to dereference
object->pointer. Thus, the value of object->pointer could be accessed
concurrently as noticed by KCSAN,
BUG: KCSAN: data-race in crc32_le_base / do_raw_spin_lock
write to 0xffffb0ea683a7d50 of 4 bytes by task 23575 on cpu 12:
do_raw_spin_lock+0x114/0x200
debug_spin_lock_after at kernel/locking/spinlock_debug.c:91
(inlined by) do_raw_spin_lock at kernel/locking/spinlock_debug.c:115
_raw_spin_lock+0x40/0x50
__handle_mm_fault+0xa9e/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
read to 0xffffb0ea683a7d50 of 4 bytes by task 839 on cpu 60:
crc32_le_base+0x67/0x350
crc32_le_base+0x67/0x350:
crc32_body at lib/crc32.c:106
(inlined by) crc32_le_generic at lib/crc32.c:179
(inlined by) crc32_le at lib/crc32.c:197
kmemleak_scan+0x528/0xd90
update_checksum at mm/kmemleak.c:1172
(inlined by) kmemleak_scan at mm/kmemleak.c:1497
kmemleak_scan_thread+0xcc/0xfa
kthread+0x1e0/0x200
ret_from_fork+0x27/0x50
If a shattered value was returned due to a data race, it will be
corrected in the next scan. Thus, let KCSAN ignore all reads in the
region to silence KCSAN in case the write side is non-atomic.
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Qian Cai <cai@lca.pw>
---
mm/kmemleak.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index e362dc3d2028..5e252d91eb14 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1169,8 +1169,10 @@ static bool update_checksum(struct kmemleak_object *object)
u32 old_csum = object->checksum;
kasan_disable_current();
+ kcsan_disable_current();
object->checksum = crc32(0, (void *)object->pointer, object->size);
kasan_enable_current();
+ kcsan_enable_current();
return object->checksum != old_csum;
}
--
2.21.0 (Apple Git-122.2)
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/kmemleak: silence KCSAN splats in checksum
2020-03-17 18:27 [PATCH] mm/kmemleak: silence KCSAN splats in checksum Qian Cai
@ 2020-03-17 18:41 ` Marco Elver
2020-03-18 8:51 ` Catalin Marinas
1 sibling, 0 replies; 3+ messages in thread
From: Marco Elver @ 2020-03-17 18:41 UTC (permalink / raw)
To: Qian Cai
Cc: Andrew Morton, catalin.marinas, Linux Memory Management List, LKML
On Tue, 17 Mar 2020 at 19:28, Qian Cai <cai@lca.pw> wrote:
>
> Even if KCSAN is disabled for kmemleak, update_checksum() could still
> call crc32() (which is outside of kmemleak.c) to dereference
> object->pointer. Thus, the value of object->pointer could be accessed
> concurrently as noticed by KCSAN,
>
> BUG: KCSAN: data-race in crc32_le_base / do_raw_spin_lock
>
> write to 0xffffb0ea683a7d50 of 4 bytes by task 23575 on cpu 12:
> do_raw_spin_lock+0x114/0x200
> debug_spin_lock_after at kernel/locking/spinlock_debug.c:91
> (inlined by) do_raw_spin_lock at kernel/locking/spinlock_debug.c:115
> _raw_spin_lock+0x40/0x50
> __handle_mm_fault+0xa9e/0xd00
> handle_mm_fault+0xfc/0x2f0
> do_page_fault+0x263/0x6f9
> page_fault+0x34/0x40
>
> read to 0xffffb0ea683a7d50 of 4 bytes by task 839 on cpu 60:
> crc32_le_base+0x67/0x350
> crc32_le_base+0x67/0x350:
> crc32_body at lib/crc32.c:106
> (inlined by) crc32_le_generic at lib/crc32.c:179
> (inlined by) crc32_le at lib/crc32.c:197
> kmemleak_scan+0x528/0xd90
> update_checksum at mm/kmemleak.c:1172
> (inlined by) kmemleak_scan at mm/kmemleak.c:1497
> kmemleak_scan_thread+0xcc/0xfa
> kthread+0x1e0/0x200
> ret_from_fork+0x27/0x50
>
> If a shattered value was returned due to a data race, it will be
> corrected in the next scan. Thus, let KCSAN ignore all reads in the
> region to silence KCSAN in case the write side is non-atomic.
>
> Suggested-by: Marco Elver <elver@google.com>
> Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Marco Elver <elver@google.com>
Thanks,
-- Marco
> ---
> mm/kmemleak.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index e362dc3d2028..5e252d91eb14 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -1169,8 +1169,10 @@ static bool update_checksum(struct kmemleak_object *object)
> u32 old_csum = object->checksum;
>
> kasan_disable_current();
> + kcsan_disable_current();
> object->checksum = crc32(0, (void *)object->pointer, object->size);
> kasan_enable_current();
> + kcsan_enable_current();
>
> return object->checksum != old_csum;
> }
> --
> 2.21.0 (Apple Git-122.2)
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/kmemleak: silence KCSAN splats in checksum
2020-03-17 18:27 [PATCH] mm/kmemleak: silence KCSAN splats in checksum Qian Cai
2020-03-17 18:41 ` Marco Elver
@ 2020-03-18 8:51 ` Catalin Marinas
1 sibling, 0 replies; 3+ messages in thread
From: Catalin Marinas @ 2020-03-18 8:51 UTC (permalink / raw)
To: Qian Cai; +Cc: akpm, elver, linux-mm, linux-kernel
On Tue, Mar 17, 2020 at 02:27:54PM -0400, Qian Cai wrote:
> Even if KCSAN is disabled for kmemleak, update_checksum() could still
> call crc32() (which is outside of kmemleak.c) to dereference
> object->pointer. Thus, the value of object->pointer could be accessed
> concurrently as noticed by KCSAN,
>
> BUG: KCSAN: data-race in crc32_le_base / do_raw_spin_lock
>
> write to 0xffffb0ea683a7d50 of 4 bytes by task 23575 on cpu 12:
> do_raw_spin_lock+0x114/0x200
> debug_spin_lock_after at kernel/locking/spinlock_debug.c:91
> (inlined by) do_raw_spin_lock at kernel/locking/spinlock_debug.c:115
> _raw_spin_lock+0x40/0x50
> __handle_mm_fault+0xa9e/0xd00
> handle_mm_fault+0xfc/0x2f0
> do_page_fault+0x263/0x6f9
> page_fault+0x34/0x40
>
> read to 0xffffb0ea683a7d50 of 4 bytes by task 839 on cpu 60:
> crc32_le_base+0x67/0x350
> crc32_le_base+0x67/0x350:
> crc32_body at lib/crc32.c:106
> (inlined by) crc32_le_generic at lib/crc32.c:179
> (inlined by) crc32_le at lib/crc32.c:197
> kmemleak_scan+0x528/0xd90
> update_checksum at mm/kmemleak.c:1172
> (inlined by) kmemleak_scan at mm/kmemleak.c:1497
> kmemleak_scan_thread+0xcc/0xfa
> kthread+0x1e0/0x200
> ret_from_fork+0x27/0x50
>
> If a shattered value was returned due to a data race, it will be
> corrected in the next scan. Thus, let KCSAN ignore all reads in the
> region to silence KCSAN in case the write side is non-atomic.
>
> Suggested-by: Marco Elver <elver@google.com>
> Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-03-18 8:51 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-03-17 18:27 [PATCH] mm/kmemleak: silence KCSAN splats in checksum Qian Cai
2020-03-17 18:41 ` Marco Elver
2020-03-18 8:51 ` Catalin Marinas
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).