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tmpfs: fix oops on mounts with mpol=default 

Fix an 'oops' when a tmpfs mount point is mounted with the mpol=default
mempolicy.

Upon remounting a tmpfs mount point with 'mpol=default' option, the mount
code crashed with a null pointer dereference.  The initial problem report
was on 2.6.27, but the problem exists in mainline 2.6.34-rc as well.  On
examining the code, we see that mpol_new returns NULL if default mempolicy
was requested.  This 'NULL' mempolicy is accessed to store the node mask
resulting in oops.

The following patch fixes it.

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Acked-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Ravikiran G Thirumalai 2010-03-23 13:35:28 -07:00 committed by Linus Torvalds
parent 8c363afe94
commit 413b43deab
1 changed files with 7 additions and 2 deletions
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9
mm/mempolicy.c
View File

@ -2215,10 +2215,15 @@ int mpol_parse_str(char *str, struct mempolicy **mpol, int no_context)
goto out;
mode = MPOL_PREFERRED;
break;
case MPOL_DEFAULT:
/*
* Insist on a empty nodelist
*/
if (!nodelist)
err = 0;
goto out;
/*
* case MPOL_BIND: mpol_new() enforces non-empty nodemask.
* case MPOL_DEFAULT: mpol_new() enforces empty nodemask, ignores flags.
*/
}