blob: 1fd85e5879c500ab4ced3c19404b5d8011a041cb [file] [log] [blame]
From 01fbab26857fe17301e98bc8769c93fc5861ac33 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 30 Jan 2020 22:11:07 -0800
Subject: [PATCH] mm/mempolicy.c: fix out of bounds write in mpol_parse_str()
commit c7a91bc7c2e17e0a9c8b9745a2cb118891218fd1 upstream.
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: 095f1fc4ebf3 ("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>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index ec80a36b324e..c8c8ec6e788a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2792,6 +2792,9 @@ 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';
@@ -2802,9 +2805,6 @@ 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;
--
2.7.4