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SubjectRE: [syzbot] WARNING in exit_tasks_rcu_finish
Date
On Tue, Jun 14, 2022 at 12:52:23AM +0000, Zhang, Qiang1 wrote:
> On Mon, Jun 13, 2022 at 04:42:07PM -0700, Kees Cook wrote:
> > On Mon, Jun 13, 2022 at 10:36:07AM -0700, syzbot wrote:
> > > Hello,
> > >
> > > syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> > >
> > > Reported-and-tested-by:
> > > syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com
> >
> > Looks like the patch solved the reproducer. :)
>
> >For one of the two possible ways to make the bug happen. ;-)
> >
> >Still, good on Qiang for identifying one of the paths! Not just anyone can do that.
>
> Thanks Paul, yes this patch can solved the reproducer and I also test it.
>
> I compiled "bpf_test" according to the c file in the following link
>
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=148207bff00000
>
> Not apply this patch, this calltrace reproduce
>
> root@qemux86-64:/# ./bpf_test
> ^C
> root@qemux86-64:/# dmesg
> [ 147.017232] ------------[ cut here ]------------ [ 147.017234]
> WARNING: CPU: 3 PID: 21586 at kernel/rcu/tasks.h:1664
> exit_tasks_rcu_finish+0xbf/0x100 [ 147.017245] Modules linked in:
> [ 147.017249] CPU: 3 PID: 21586 Comm: bpf_test Not tainted
> 5.19.0-rc1-next-20220610-yoctodev-standard #204 [ 147.017253]
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 147.017256]
> RIP: 0010:exit_tasks_rcu_finish+0xbf/0x100
> [ 147.017261] Code: 03 00 00 85 c0 75 59 f0 83 44 24 fc 00 49 8d bc
> 24 41 03 00 00 e8 21 09 2b 00 41 0f b6 84 24 41 03 00 00 83 e0 01 08
> d8 74 11 <0f> 8 [ 147.017264] RSP: 0018:ffff88810ccd7af0 EFLAGS:
> 00010202 [ 147.017268] RAX: 0000000000000001 RBX: 0000000000000201
> RCX: ffffffff897ab52f [ 147.017271] RDX: 1ffff1102181d7c8 RSI:
> 0000000000000000 RDI: ffff88810c0ebe41 [ 147.017274] RBP:
> ffff88810ccd7b08 R08: ffffffff897ab510 R09: 0000000000000000 [
> 147.017277] R10: ffffffff8c407bbf R11: 0000000000000000 R12:
> ffff88810c0ebb00 [ 147.017279] R13: ffff88810c0ebe38 R14:
> ffff88810ccd7b78 R15: ffff88810ccd76b0 [ 147.017282] FS:
> 0000000000000000(0000) GS:ffff88815a000000(0000) knlGS:0000000000000000 [ 147.017287] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 147.017289] CR2: 0000000000000000 CR3: 000000011ac16000 CR4: 00000000001506e0 [ 147.017292] Call Trace:
> [ 147.017294] <TASK>
> [ 147.017297] do_exit+0xe9a/0x13a0
> [ 147.017305] ? mm_update_next_owner+0x450/0x450 [ 147.017309] ?
> lock_downgrade+0x410/0x410 [ 147.017313] ?
> lock_contended+0x790/0x790 [ 147.017317] ?
> rcu_read_lock_held_common+0x1e/0x60
> [ 147.017324] do_group_exit+0x71/0x150 [ 147.017329]
> get_signal+0x1319/0x1340 [ 147.017334] ?
> futex_wait_setup+0x180/0x180 [ 147.017341] ?
> exit_signals+0x4c0/0x4c0 [ 147.017345] ? futex_wake+0x29e/0x2e0 [
> 147.017351] arch_do_signal_or_restart+0x9c/0xc60
> [ 147.017357] ? rcu_read_lock_sched_held+0x60/0xd0
> [ 147.017361] ? rcu_read_lock_bh_held+0xb0/0xb0 [ 147.017367] ?
> get_sigframe_size+0x20/0x20 [ 147.017371] ? do_futex+0x1a2/0x240 [
> 147.017375] ? __ia32_sys_get_robust_list+0x240/0x240
> [ 147.017378] ? __context_tracking_exit+0x91/0xa0 [ 147.017385] ?
> lock_downgrade+0x410/0x410 [ 147.017390] ?
> __x64_sys_futex+0x125/0x2b0 [ 147.017393] ?
> rcu_read_lock_held_common+0x1e/0x60
> [ 147.017399] ? lockdep_hardirqs_on_prepare+0x13/0x230
> [ 147.017403] ? exit_to_user_mode_prepare+0x151/0x240
> [ 147.017409] exit_to_user_mode_prepare+0x16c/0x240
> [ 147.017415] syscall_exit_to_user_mode+0x1e/0x70
> [ 147.017419] do_syscall_64+0x50/0x90 [ 147.017423]
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
> [ 147.017427] RIP: 0033:0x7f780e668fbd [ 147.017431] Code: Unable to
> access opcode bytes at RIP 0x7f780e668f93.
> [ 147.017433] RSP: 002b:00007f780e55bd48 EFLAGS: 00000246 ORIG_RAX:
> 00000000000000ca [ 147.017437] RAX: fffffffffffffe00 RBX:
> 00007f780e55c640 RCX: 00007f780e668fbd [ 147.017440] RDX:
> 0000000000000000 RSI: 0000000000000080 RDI: 000055ed9f3a8088 [
> 147.017442] RBP: 00007f780e55bd60 R08: 0000000100000001 R09:
> 0000000100000001 [ 147.017445] R10: 0000000000000000 R11:
> 0000000000000246 R12: fffffffffffffeb0 [ 147.017447] R13:
> 0000000000000000 R14: 00007ffe5dcf20a0 R15: 00007f780e53c000 [
> 147.017455] </TASK> [ 147.017458] irq event stamp: 0 [ 147.017460]
> hardirqs last enabled at (0): [<0000000000000000>] 0x0 [ 147.017463]
> hardirqs last disabled at (0): [<ffffffff896b5990>]
> copy_process+0xe30/0x35f0 [ 147.017467] softirqs last enabled at
> (0): [<ffffffff896b5990>] copy_process+0xe30/0x35f0 [ 147.017470]
> softirqs last disabled at (0): [<0000000000000000>] 0x0 [ 147.017473]
> ---[ end trace 0000000000000000 ]---
>
> Apply this patch , this problem not reproduce.
>
>Thank you very much! May I apply your Tested-by?

Thanks, I am very willing

>
> Thanx, Paul

> Thanks
> Zqiang
>
> >
> > Thanx, Paul
> >
> > > Tested on:
> > >
> > > commit: 6d0c8068 Add linux-next specific files for 20220610
> > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20220610
> > > console output:
> > > https://syzkaller.appspot.com/x/log.txt?x=12d068eff00000
> > > kernel config:
> > > https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
> > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > patch: https://syzkaller.appspot.com/x/patch.diff?x=147f47c8080000
> > >
> > > Note: testing is done by a robot and is best-effort only.
> >
> > You can see the dashboard link above for testing details...
> >
> > --
> > Kees Cook

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