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mm/mempolicy.c: fix out of bounds write in mpol_parse_str()

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What we are trying to do is change the '=' character to a NUL terminator
and then at the end of the function we restore it back to an '='.  The
problem is there are two error paths where we jump to the end of the
function before we have replaced the '=' with NUL.

We end up putting the '=' in the wrong place (possibly one element
before the start of the buffer).

Link: http://lkml.kernel.org/r/20200115055426.vdjwvry44nfug7yy@kili.mountain
Reported-by: syzbot+e64a13c5369a194d67df@syzkaller.appspotmail.com
Fixes: 095f1fc4eb ("mempolicy: rework shmem mpol parsing and display")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Dmitry Vyukov <dvyukov@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.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:
Dan Carpenter 2020-01-30 22:11:07 -08:00 committed by Linus Torvalds
parent 68f23b8906
commit c7a91bc7c2
1 changed files with 3 additions and 3 deletions
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6
mm/mempolicy.c
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@ -2821,6 +2821,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
char *flags = strchr(str, '=');
int err = 1, mode;
if (flags)
*flags++ = '\0'; /* terminate mode string */
if (nodelist) {
/* NUL-terminate mode or flags string */
*nodelist++ = '\0';
@ -2831,9 +2834,6 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
} else
nodes_clear(nodes);
if (flags)
*flags++ = '\0'; /* terminate mode string */
mode = match_string(policy_modes, MPOL_MAX, str);
if (mode < 0)
goto out;