From: Dan Carpenter <dan.carpenter@oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
syzbot <syzbot+e64a13c5369a194d67df@syzkaller.appspotmail.com>,
aarcange@redhat.com, hughd@google.com, mhocko@suse.com,
syzkaller-bugs@googlegroups.com, vbabka@suse.cz,
viro@zeniv.linux.org.uk, yang.shi@linux.alibaba.com
Subject: [PATCH] mm/mempolicy.c: Fix out of bounds write in mpol_parse_str()
Date: Wed, 15 Jan 2020 08:54:26 +0300 [thread overview]
Message-ID: <20200115055426.vdjwvry44nfug7yy@kili.mountain> (raw)
In-Reply-To: <0000000000006a8b8f059c24672a@google.com>
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).
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>
---
mm/mempolicy.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 067cf7d3daf5..1340c5c496b5 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2817,6 +2817,9 @@ 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';
@@ -2827,9 +2830,6 @@ 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;
--
2.11.0
next prev parent reply other threads:[~2020-01-15 5:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 2:24 KASAN: slab-out-of-bounds Write in mpol_parse_str syzbot
2020-01-15 5:54 ` Dan Carpenter [this message]
2020-01-15 12:54 ` [PATCH] mm/mempolicy.c: Fix out of bounds write in mpol_parse_str() Vlastimil Babka
2020-01-15 12:57 ` Dmitry Vyukov
2020-01-15 15:03 ` Michal Hocko
2020-01-15 15:14 ` Dmitry Vyukov
2020-01-15 19:05 ` Michal Hocko
2020-01-16 5:41 ` Dmitry Vyukov
2020-01-16 7:39 ` Michal Hocko
2020-01-16 10:13 ` Dmitry Vyukov
2020-01-16 11:51 ` Michal Hocko
2020-01-16 12:41 ` Dmitry Vyukov
2020-01-16 14:05 ` Michal Hocko
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