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x86: Simplify bound checks in the MTRR code

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The current bound checks for copy_from_user in the MTRR driver are
not as obvious as they could be, and gcc agrees with that.

This patch simplifies the boundary checks to the point that gcc can
now prove to itself that the copy_from_user() is never going past
its bounds.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20090926205150.30797709@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Arjan van de Ven 2009-09-26 20:51:50 +02:00 committed by Ingo Molnar
parent 0d18b2e34b
commit 11879ba5d9
1 changed files with 12 additions and 5 deletions
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17
arch/x86/kernel/cpu/mtrr/if.c
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@ -96,17 +96,24 @@ mtrr_write(struct file *file, const char __user *buf, size_t len, loff_t * ppos)
unsigned long long base, size;
char *ptr;
char line[LINE_SIZE];
int length;
size_t linelen;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!len)
return -EINVAL;
memset(line, 0, LINE_SIZE);
if (len > LINE_SIZE)
len = LINE_SIZE;
if (copy_from_user(line, buf, len - 1))
length = len;
length--;
if (length > LINE_SIZE - 1)
length = LINE_SIZE - 1;
if (length < 0)
return -EINVAL;
if (copy_from_user(line, buf, length))
return -EFAULT;
linelen = strlen(line);