From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 61678d28d4a45ef376f5d02a839cc37509ae9281 ]
syzbot reported an out-of-bound access in em_nbyte. As initially analyzed by Eric, this is because em_nbyte sets its own em->datalen in em_nbyte_change() other than the one specified by user, but this value gets overwritten later by its caller tcf_em_validate(). We should leave em->datalen untouched to respect their choices.
I audit all the in-tree ematch users, all of those implement ->change() set em->datalen, so we can just avoid setting it twice in this case.
Reported-and-tested-by: syzbot+5af9a90dad568aa9f611@syzkaller.appspotmail.com Reported-by: syzbot+2f07903a5b05e7f36410@syzkaller.appspotmail.com Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: Eric Dumazet eric.dumazet@gmail.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/ematch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/sched/ematch.c +++ b/net/sched/ematch.c @@ -267,12 +267,12 @@ static int tcf_em_validate(struct tcf_pr } em->data = (unsigned long) v; } + em->datalen = data_len; } }
em->matchid = em_hdr->matchid; em->flags = em_hdr->flags; - em->datalen = data_len; em->net = net;
err = 0;