On Thu, Aug 30, 2018 at 7:19 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Thu, Aug 30, 2018 at 2:52 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: >>>>>> Hello, >>>>>> >>>>>> syzbot found the following crash on: >>>>>> >>>>>> HEAD commit: 5b394b2ddf03 Linux 4.19-rc1 >>>>>> git tree: upstream >>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=14f4d8e1400000 >>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=49927b422dcf0b29 >>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=45a34334c61a8ecf661d >>>>>> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13127e5a400000 >>>>>> >>>>>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>>>>> Reported-by: syzbot+45a34334c61a8ecf661d@xxxxxxxxxxxxxxxxxxxxxxxxx >>>>>> >>>>>> IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready >>>>>> IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready >>>>>> IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready >>>>>> 8021q: adding VLAN 0 to HW filter on device team0 >>>>>> ================================================================== >>>>>> BUG: KASAN: stack-out-of-bounds in schedule_debug kernel/sched/core.c:3285 >>>>>> [inline] >>>>>> BUG: KASAN: stack-out-of-bounds in __schedule+0x1977/0x1df0 >>>>>> kernel/sched/core.c:3395 >>>>>> Read of size 8 at addr ffff8801ad090000 by task syz-executor0/4718 >>>>> >>>>> Weird, can you please help me decipher this? So here KASAN complains about >>>>> wrong memory access in the scheduler. >>> >>> This looks like a result of a previous bad silent memory corruption. >>> >>> The KASAN report says there is a stack out-of-bounds in scheduler. And >>> that if followed by slab corruption report in another task. >>> >>> fs/jbd2/transaction.c happens to be the first meaningful file in this >>> crash, and so that's where it is attributed to. >>> >>> Rerunning the reproducer several times can maybe give some better >>> glues, or maybe not, maybe they all will look equally puzzling. >>> >>> This part of the repro looks familiar: >>> >>> r1 = bpf$MAP_CREATE(0x0, &(0x7f0000002e40)={0x12, 0x0, 0x4, 0x6e, 0x0, >>> 0x1}, 0x68) >>> bpf$MAP_UPDATE_ELEM(0x2, &(0x7f0000000180)={r1, &(0x7f0000000000), >>> &(0x7f0000000140)}, 0x20) >>> >>> We had exactly such consequences of a bug in bpf map very recently, >>> but that was claimed to be fixed. Maybe not completely? >>> +bpf maintainers >> >> Looks like syzbot found this in Linus tree with HEAD commit 5b394b2ddf03 ("Linux 4.19-rc1") >> one day later net PR got merged via 050cdc6c9501 ("Merge git://git.kernel.org/pub/..."). >> >> This PR contained a couple of fixes I did on sockmap code during audit such as: >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b845c898b2f1ea458d5453f0fa1da6e2dfce3bb4 >> >> Looking at the reproducer syzkaller found it contains: >> >> r1 = bpf$MAP_CREATE(0x0, &(0x7f0000002e40)={0x12, 0x0, 0x4, 0x6e, 0x0, 0x1}, 0x68) >> ^^^ >> >> So it found the crash with map type of sock hash and key size of 0x0 (which is invalid), >> where subsequent map update triggered the corruption. I just did a 'syz test' and it >> wasn't able to trigger the crash anymore. >> >> #syz fix: bpf, sockmap: fix sock_hash_alloc and reject zero-sized keys This crash looks related: https://groups.google.com/d/msg/syzkaller-bugs/luviyHUQ9N4/dmgK2OmLBAAJ
