On Mon, Jun 10, 2019 at 11:27 PM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > > syzbot <syzbot+f625baafb9a1c4bfc3f6@xxxxxxxxxxxxxxxxxxxxxxxxx> writes: > > > syzbot has bisected this bug to: > > > > commit e9db4ef6bf4ca9894bb324c76e01b8f1a16b2650 > > Author: John Fastabend <john.fastabend@xxxxxxxxx> > > Date: Sat Jun 30 13:17:47 2018 +0000 > > > > bpf: sockhash fix omitted bucket lock in sock_close > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15e978e1a00000 > > start commit: 38e406f6 Merge git://git.kernel.org/pub/scm/linux/kernel/g.. > > git tree: net > > final crash: https://syzkaller.appspot.com/x/report.txt?x=17e978e1a00000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=13e978e1a00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=60564cb52ab29d5b > > dashboard link: https://syzkaller.appspot.com/bug?extid=f625baafb9a1c4bfc3f6 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1193d81ea00000 > > > > Reported-by: syzbot+f625baafb9a1c4bfc3f6@xxxxxxxxxxxxxxxxxxxxxxxxx > > Fixes: e9db4ef6bf4c ("bpf: sockhash fix omitted bucket lock in sock_close") > > > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > How is mm_update_next_owner connected to bpf? There seems to be a nasty bug in bpf that causes assorted crashes throughout the kernel for some time. I've seen a bunch of reproducers that do something with bpf and then cause a random crash. The more unpleasant ones are the bugs without reproducers, because for these we don't have a way to link them back to the bpf bug but they are still hanging there without good explanation, e.g. maybe a part of one-off crashes in moderation: https://syzkaller.appspot.com/upstream#moderation2 Such bugs are nice to fix asap to not produce more and more random crash reports. Hillf, did you understand the mechanics of this bug and memory corruption? A good question is why this was unnoticed by KASAN. If we could make it catch it at the point of occurrence, then it would be a single bug report clearly attributed to bpf rather then dozens of assorted crashes.
