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Security: round mmap hint address above mmap_min_addr

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If mmap_min_addr is set and a process attempts to mmap (not fixed) with a
non-null hint address less than mmap_min_addr the mapping will fail the
security checks.  Since this is just a hint address this patch will round
such a hint address above mmap_min_addr.

gcj was found to try to be very frugal with vm usage and give hint addresses
in the 8k-32k range.  Without this patch all such programs failed and with
the patch they happily get a higher address.

This patch is wrappad in CONFIG_SECURITY since mmap_min_addr doesn't exist
without it and there would be no security check possible no matter what.  So
we should not bother compiling in this rounding if it is just a waste of
time.

Signed-off-by: Eric Paris <[email protected]>
Signed-off-by: James Morris <[email protected]>
This commit is contained in:
Eric Paris 2007-11-26 18:47:40 -05:00 • committed by James Morris
commit 7cd94146cd
3 changed files with 22 additions and 0 deletions
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3
mm/mmap.c
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@ -912,6 +912,9 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
if (!len)
return -EINVAL;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
error = arch_mmap_check(addr, len, flags);
if (error)
return error;

3
mm/nommu.c
View file

@ -829,6 +829,9 @@ unsigned long do_mmap_pgoff(struct file *file,
void *result;
int ret;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
/* decide whether we should attempt the mapping, and if so what sort of
* mapping */
ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,