RE: [syzbot] WARNING in exit_tasks_rcu_finish
From: Zhang, Qiang1
Date: Mon Jun 13 2022 - 20:52:34 EST
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@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> 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.
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