From: Dan Carpenter dan.carpenter@oracle.com
stable inclusion from stable-v4.19.102 commit 732ecd4aad51d336b49b9be431219d173ac826c8 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6L0EC CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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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: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: ZhangPeng zhangpeng362@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Reviewed-by: tong tiangen tongtiangen@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 4cac46d56f38..4769ed2ed7f3 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2886,6 +2886,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol) char *flags = strchr(str, '='); int err = 1;
+ if (flags) + *flags++ = '\0'; /* terminate mode string */ + if (nodelist) { /* NUL-terminate mode or flags string */ *nodelist++ = '\0'; @@ -2896,9 +2899,6 @@ int mpol_parse_str(char *str, struct mempolicy **mpol) } else nodes_clear(nodes);
- if (flags) - *flags++ = '\0'; /* terminate mode string */ - for (mode = 0; mode < MPOL_MAX; mode++) { if (!strcmp(str, policy_modes[mode])) { break;