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Message-Id: <20200203161905.207969687@linuxfoundation.org>
Date: Mon, 3 Feb 2020 16:20:33 +0000
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org,
syzbot+e64a13c5369a194d67df@...kaller.appspotmail.com,
Dan Carpenter <dan.carpenter@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Michal Hocko <mhocko@...nel.org>,
Lee Schermerhorn <lee.schermerhorn@...com>,
Andrea Arcangeli <aarcange@...hat.com>,
Hugh Dickins <hughd@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.5 13/23] mm/mempolicy.c: fix out of bounds write in mpol_parse_str()
From: Dan Carpenter <dan.carpenter@...cle.com>
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@...kaller.appspotmail.com
Fixes: 095f1fc4ebf3 ("mempolicy: rework shmem mpol parsing and display")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Dmitry Vyukov <dvyukov@...gle.com>
Cc: Michal Hocko <mhocko@...nel.org>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Lee Schermerhorn <lee.schermerhorn@...com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
mm/mempolicy.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2821,6 +2821,9 @@ int mpol_parse_str(char *str, struct mem
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 mem
} else
nodes_clear(nodes);
- if (flags)
- *flags++ = '\0'; /* terminate mode string */
-
mode = match_string(policy_modes, MPOL_MAX, str);
if (mode < 0)
goto out;
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