net_sched: fix datalen for ematch
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: 1da177e4 ("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>
parent
42c9bdae
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