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mm: mremap: validate input before taking lock

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This patch is very similar to commit 84d96d8976 ("mm: madvise:
complete input validation before taking lock"): perform some basic
validation of the input to mremap() before taking the
&current->mm->mmap_sem lock.

This also makes the MREMAP_FIXED => MREMAP_MAYMOVE dependency slightly
more explicit.

Signed-off-by: Rasmus Villemoes <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Rasmus Villemoes 2013-07-08 15:59:48 -07:00 • committed by Linus Torvalds
commit 9a2458a633
1 changed files with 10 additions and 8 deletions
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18
mm/mremap.c
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@ -456,13 +456,14 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
unsigned long charged = 0;
bool locked = false;
down_write(&current->mm->mmap_sem);
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
goto out;
return ret;
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
return ret;
if (addr & ~PAGE_MASK)
goto out;
return ret;
old_len = PAGE_ALIGN(old_len);
new_len = PAGE_ALIGN(new_len);
@ -473,12 +474,13 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
* a zero new-len is nonsensical.
*/
if (!new_len)
goto out;
return ret;
down_write(&current->mm->mmap_sem);
if (flags & MREMAP_FIXED) {
if (flags & MREMAP_MAYMOVE)
ret = mremap_to(addr, old_len, new_addr, new_len,
&locked);
ret = mremap_to(addr, old_len, new_addr, new_len,
&locked);
goto out;
}