* [PATCH] ARM: poison_init_mem: fixed underflow in loop
@ 2013-02-20 11:52 Enrico Scholz
2013-02-20 21:56 ` Stephen Boyd
0 siblings, 1 reply; 2+ messages in thread
From: Enrico Scholz @ 2013-02-20 11:52 UTC (permalink / raw)
To: linux-arm-kernel
When initmemory ends at an odd address, the loop variable in
poison_init_mem() will underflow which causes overriding of valid
memory. Such situations are not a theoretical issue only but
exist in practice:
| [ 0.000000] .init : 0xc0634000 - 0xc0c215ab (6070 kB)
Patch makes a simple division instead of DIV_ROUND_UP() because latter
can override some bytes after .init.
Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz•de>
---
arch/arm/mm/init.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index ad722f1..c431a2d 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -449,7 +449,8 @@ static inline int free_area(unsigned long pfn, unsigned long end, char *s)
static inline void poison_init_mem(void *s, size_t count)
{
u32 *p = (u32 *)s;
- for (; count != 0; count -= 4)
+ count /= sizeof(*p);
+ for (; count != 0; count--)
*p++ = 0xe7fddef0;
}
--
1.8.1.2
^ permalink raw reply related [flat|nested] 2+ messages in thread* [PATCH] ARM: poison_init_mem: fixed underflow in loop
2013-02-20 11:52 [PATCH] ARM: poison_init_mem: fixed underflow in loop Enrico Scholz
@ 2013-02-20 21:56 ` Stephen Boyd
0 siblings, 0 replies; 2+ messages in thread
From: Stephen Boyd @ 2013-02-20 21:56 UTC (permalink / raw)
To: linux-arm-kernel
On 2/20/2013 3:52 AM, Enrico Scholz wrote:
> When initmemory ends at an odd address, the loop variable in
> poison_init_mem() will underflow which causes overriding of valid
> memory. Such situations are not a theoretical issue only but
> exist in practice:
>
> | [ 0.000000] .init : 0xc0634000 - 0xc0c215ab (6070 kB)
>
> Patch makes a simple division instead of DIV_ROUND_UP() because latter
> can override some bytes after .init.
>
> Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz•de>
> ---
> arch/arm/mm/init.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index ad722f1..c431a2d 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -449,7 +449,8 @@ static inline int free_area(unsigned long pfn, unsigned long end, char *s)
> static inline void poison_init_mem(void *s, size_t count)
> {
> u32 *p = (u32 *)s;
> - for (; count != 0; count -= 4)
> + count /= sizeof(*p);
> + for (; count != 0; count--)
> *p++ = 0xe7fddef0;
> }
>
Sigh. I really screwed that up badly. I wonder if we should instead
PAGE_ALIGN() the end address similar to what we're doing for the initrd
and then put a BUG_ON() inside poison_init_mem() that catches none page
aligned sizes.
--
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2013-02-20 11:52 [PATCH] ARM: poison_init_mem: fixed underflow in loop Enrico Scholz
2013-02-20 21:56 ` Stephen Boyd
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