From: Dan Carpenter <dan.carpenter@oracle.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@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: Yang Yingliang <yangyingliang@huawei.com> --- mm/mempolicy.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index df74d13..e8a5f22 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2860,6 +2860,9 @@ 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'; @@ -2870,9 +2873,6 @@ 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; -- 1.8.3