Commit 8d77a6d1 authored by Xishi Qiu's avatar Xishi Qiu Committed by Linus Torvalds
Browse files

kasan: fix last shadow judgement in memory_is_poisoned_16()

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: default avatarXishi Qiu <>
Acked-by: default avatarAndrey Ryabinin <>
Cc: Andrey Konovalov <>
Cc: Rusty Russell <>
Cc: Michal Marek <>
Cc: <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 3aaf14da
......@@ -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);
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment