* [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() @ 2015-09-08 12:12 Xishi Qiu 2015-09-09 6:40 ` long.wanglong 2015-09-09 10:01 ` Andrey Ryabinin 0 siblings, 2 replies; 6+ messages in thread From: Xishi Qiu @ 2015-09-08 12:12 UTC (permalink / raw) To: Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang Cc: Linux MM, LKML The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the memory is aligned on 8, then the shadow takes only 2 bytes. So we check "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". But the code "if (likely(!last_byte))" is wrong judgement. e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will continue to call "memory_is_poisoned_1(addr + 15);" Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> --- mm/kasan/kasan.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 7b28e9c..8da2114 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) if (unlikely(*shadow_addr)) { u16 shadow_first_bytes = *(u16 *)shadow_addr; - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; if (unlikely(shadow_first_bytes)) return true; - if (likely(!last_byte)) + if (likely(IS_ALIGNED(addr, 8))) return false; return memory_is_poisoned_1(addr + 15); -- 1.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() 2015-09-08 12:12 [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() Xishi Qiu @ 2015-09-09 6:40 ` long.wanglong 2015-09-09 7:43 ` Xishi Qiu 2015-09-09 8:30 ` Andrey Ryabinin 2015-09-09 10:01 ` Andrey Ryabinin 1 sibling, 2 replies; 6+ messages in thread From: long.wanglong @ 2015-09-09 6:40 UTC (permalink / raw) To: Xishi Qiu, ryabinin.a.a Cc: Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang, Linux MM, LKML, Wang Long On 2015/9/8 20:12, Xishi Qiu wrote: > The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the > memory is aligned on 8, then the shadow takes only 2 bytes. So we check > "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". > But the code "if (likely(!last_byte))" is wrong judgement. > > e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will > continue to call "memory_is_poisoned_1(addr + 15);" > > Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> > --- > mm/kasan/kasan.c | 3 +-- > 1 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 7b28e9c..8da2114 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) > > if (unlikely(*shadow_addr)) { > u16 shadow_first_bytes = *(u16 *)shadow_addr; > - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; > > if (unlikely(shadow_first_bytes)) > return true; > > - if (likely(!last_byte)) > + if (likely(IS_ALIGNED(addr, 8))) > return false; > > return memory_is_poisoned_1(addr + 15); > Hi, I also notice this problem, how about another method to fix it: diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 5d65d06..6a20dda 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -140,7 +140,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) if (unlikely(shadow_first_bytes)) return true; - if (likely(!last_byte)) + if (likely(last_byte >= 7)) return false; return memory_is_poisoned_1(addr + 15); This method can ensure consistency of code, for example, in memory_is_poisoned_8: static __always_inline bool memory_is_poisoned_8(unsigned long addr) { u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr); if (unlikely(*shadow_addr)) { if (memory_is_poisoned_1(addr + 7)) return true; if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7)) return false; return unlikely(*(u8 *)shadow_addr); } return false; } Otherwise, we also should use IS_ALIGNED macro in memory_is_poisoned_8! Best Regards Wang Long -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() 2015-09-09 6:40 ` long.wanglong @ 2015-09-09 7:43 ` Xishi Qiu 2015-09-09 8:10 ` long.wanglong 2015-09-09 8:30 ` Andrey Ryabinin 1 sibling, 1 reply; 6+ messages in thread From: Xishi Qiu @ 2015-09-09 7:43 UTC (permalink / raw) To: long.wanglong Cc: ryabinin.a.a, Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang, Linux MM, LKML On 2015/9/9 14:40, long.wanglong wrote: > On 2015/9/8 20:12, Xishi Qiu wrote: >> The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the >> memory is aligned on 8, then the shadow takes only 2 bytes. So we check >> "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". >> But the code "if (likely(!last_byte))" is wrong judgement. >> >> e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will >> continue to call "memory_is_poisoned_1(addr + 15);" >> >> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> >> --- >> mm/kasan/kasan.c | 3 +-- >> 1 files changed, 1 insertions(+), 2 deletions(-) >> >> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c >> index 7b28e9c..8da2114 100644 >> --- a/mm/kasan/kasan.c >> +++ b/mm/kasan/kasan.c >> @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) >> >> if (unlikely(*shadow_addr)) { >> u16 shadow_first_bytes = *(u16 *)shadow_addr; >> - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; >> >> if (unlikely(shadow_first_bytes)) >> return true; >> >> - if (likely(!last_byte)) >> + if (likely(IS_ALIGNED(addr, 8))) >> return false; >> >> return memory_is_poisoned_1(addr + 15); >> > > Hi, > I also notice this problem, how about another method to fix it: > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 5d65d06..6a20dda 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -140,7 +140,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) > if (unlikely(shadow_first_bytes)) > return true; > > - if (likely(!last_byte)) > + if (likely(last_byte >= 7)) > return false; > > return memory_is_poisoned_1(addr + 15); > > This method can ensure consistency of code, for example, in memory_is_poisoned_8: > > static __always_inline bool memory_is_poisoned_8(unsigned long addr) > { > u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr); > > if (unlikely(*shadow_addr)) { > if (memory_is_poisoned_1(addr + 7)) > return true; > > if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7)) > return false; > > return unlikely(*(u8 *)shadow_addr); > } > > return false; > } > > Otherwise, we also should use IS_ALIGNED macro in memory_is_poisoned_8! > Hi Wanglong, How about use IS_ALIGNED instead of those code in memory_is_poisoned_8() and other functions? I think the current code looks a bit ugly. Thanks, Xishi Qiu > > Best Regards > Wang Long > > > > > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() 2015-09-09 7:43 ` Xishi Qiu @ 2015-09-09 8:10 ` long.wanglong 0 siblings, 0 replies; 6+ messages in thread From: long.wanglong @ 2015-09-09 8:10 UTC (permalink / raw) To: Xishi Qiu Cc: ryabinin.a.a, Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang, Linux MM, LKML On 2015/9/9 15:43, Xishi Qiu wrote: > On 2015/9/9 14:40, long.wanglong wrote: > >> On 2015/9/8 20:12, Xishi Qiu wrote: >>> The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the >>> memory is aligned on 8, then the shadow takes only 2 bytes. So we check >>> "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". >>> But the code "if (likely(!last_byte))" is wrong judgement. >>> >>> e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will >>> continue to call "memory_is_poisoned_1(addr + 15);" >>> >>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> >>> --- >>> mm/kasan/kasan.c | 3 +-- >>> 1 files changed, 1 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c >>> index 7b28e9c..8da2114 100644 >>> --- a/mm/kasan/kasan.c >>> +++ b/mm/kasan/kasan.c >>> @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) >>> >>> if (unlikely(*shadow_addr)) { >>> u16 shadow_first_bytes = *(u16 *)shadow_addr; >>> - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; >>> >>> if (unlikely(shadow_first_bytes)) >>> return true; >>> >>> - if (likely(!last_byte)) >>> + if (likely(IS_ALIGNED(addr, 8))) >>> return false; >>> >>> return memory_is_poisoned_1(addr + 15); >>> >> >> Hi, >> I also notice this problem, how about another method to fix it: >> >> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c >> index 5d65d06..6a20dda 100644 >> --- a/mm/kasan/kasan.c >> +++ b/mm/kasan/kasan.c >> @@ -140,7 +140,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) >> if (unlikely(shadow_first_bytes)) >> return true; >> >> - if (likely(!last_byte)) >> + if (likely(last_byte >= 7)) >> return false; >> >> return memory_is_poisoned_1(addr + 15); >> >> This method can ensure consistency of code, for example, in memory_is_poisoned_8: >> >> static __always_inline bool memory_is_poisoned_8(unsigned long addr) >> { >> u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr); >> >> if (unlikely(*shadow_addr)) { >> if (memory_is_poisoned_1(addr + 7)) >> return true; >> >> if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7)) >> return false; >> >> return unlikely(*(u8 *)shadow_addr); >> } >> >> return false; >> } >> >> Otherwise, we also should use IS_ALIGNED macro in memory_is_poisoned_8! >> > > Hi Wanglong, > > How about use IS_ALIGNED instead of those code in memory_is_poisoned_8() > and other functions? I think the current code looks a bit ugly. > I think we can use IS_ALIGNED macro in memory_is_poisoned_8 and memory_is_poisoned_16. but for functions memory_is_poisoned_2 and memory_is_poisoned_4, we can't. Wang Long > Thanks, > Xishi Qiu > >> >> Best Regards >> Wang Long >> >> >> >> >> >> . >> > > > > > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() 2015-09-09 6:40 ` long.wanglong 2015-09-09 7:43 ` Xishi Qiu @ 2015-09-09 8:30 ` Andrey Ryabinin 1 sibling, 0 replies; 6+ messages in thread From: Andrey Ryabinin @ 2015-09-09 8:30 UTC (permalink / raw) To: long.wanglong Cc: Xishi Qiu, Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang, Linux MM, LKML 2015-09-09 9:40 GMT+03:00 long.wanglong <long.wanglong@huawei.com>: > On 2015/9/8 20:12, Xishi Qiu wrote: >> The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the >> memory is aligned on 8, then the shadow takes only 2 bytes. So we check >> "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". >> But the code "if (likely(!last_byte))" is wrong judgement. >> >> e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will >> continue to call "memory_is_poisoned_1(addr + 15);" >> >> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> >> --- >> mm/kasan/kasan.c | 3 +-- >> 1 files changed, 1 insertions(+), 2 deletions(-) >> >> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c >> index 7b28e9c..8da2114 100644 >> --- a/mm/kasan/kasan.c >> +++ b/mm/kasan/kasan.c >> @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) >> >> if (unlikely(*shadow_addr)) { >> u16 shadow_first_bytes = *(u16 *)shadow_addr; >> - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK; >> >> if (unlikely(shadow_first_bytes)) >> return true; >> >> - if (likely(!last_byte)) >> + if (likely(IS_ALIGNED(addr, 8))) >> return false; >> >> return memory_is_poisoned_1(addr + 15); >> > > Hi, > I also notice this problem, how about another method to fix it: > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > index 5d65d06..6a20dda 100644 > --- a/mm/kasan/kasan.c > +++ b/mm/kasan/kasan.c > @@ -140,7 +140,7 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr) > if (unlikely(shadow_first_bytes)) > return true; > > - if (likely(!last_byte)) > + if (likely(last_byte >= 7)) I suggested to use IS_ALIGNED instead of this because it generates less code and it also more readable. ./scripts/bloat-o-meter kasan_aligned.o kasan_last_byte.o add/remove: 0/0 grow/shrink: 4/0 up/down: 20/0 (20) function old new delta __asan_store16_noabort 106 111 +5 __asan_store16 106 111 +5 __asan_load16_noabort 103 108 +5 __asan_load16 103 108 +5 > } > > return false; > } > > Otherwise, we also should use IS_ALIGNED macro in memory_is_poisoned_8! > I believe this would be a beneficial micro optimization. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() 2015-09-08 12:12 [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() Xishi Qiu 2015-09-09 6:40 ` long.wanglong @ 2015-09-09 10:01 ` Andrey Ryabinin 1 sibling, 0 replies; 6+ messages in thread From: Andrey Ryabinin @ 2015-09-09 10:01 UTC (permalink / raw) To: Xishi Qiu, Andrew Morton, Andrey Konovalov, Rusty Russell, Michal Marek, zhongjiang Cc: Linux MM, LKML, ryabinin.a.a On 09/08/2015 03:12 PM, Xishi Qiu wrote: > The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the > memory is aligned on 8, then the shadow takes only 2 bytes. So we check > "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". > But the code "if (likely(!last_byte))" is wrong judgement. > > e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will > continue to call "memory_is_poisoned_1(addr + 15);" > > Signed-off-by: Xishi Qiu <qiuxishi@huawei.com> Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a> ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-09-09 10:01 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2015-09-08 12:12 [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned_16() Xishi Qiu 2015-09-09 6:40 ` long.wanglong 2015-09-09 7:43 ` Xishi Qiu 2015-09-09 8:10 ` long.wanglong 2015-09-09 8:30 ` Andrey Ryabinin 2015-09-09 10:01 ` Andrey Ryabinin
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