Re: [syzbot] INFO: task hung in vhost_work_dev_flush
From: Stefano Garzarella
Date: Mon Feb 21 2022 - 09:12:56 EST
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
f71077a4d84b
Patch sent upstream:
https://lore.kernel.org/virtualization/20220221114916.107045-1-sgarzare@xxxxxxxxxx/T/#u
On Sat, Feb 19, 2022 at 12:23 AM syzbot
<syzbot+0abd373e2e50d704db87@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: e6251ab4551f Merge tag 'nfs-for-5.17-2' of git://git.linux..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=163caa3c700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=266de9da75c71a45
> dashboard link: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=108514a4700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ca671c700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+0abd373e2e50d704db87@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> INFO: task syz-executor117:3632 blocked for more than 143 seconds.
> Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor117 state:D stack:27512 pid: 3632 ppid: 3631 flags:0x00004002
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:4986 [inline]
> __schedule+0xab2/0x4db0 kernel/sched/core.c:6295
> schedule+0xd2/0x260 kernel/sched/core.c:6368
> schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857
> do_wait_for_common kernel/sched/completion.c:85 [inline]
> __wait_for_common kernel/sched/completion.c:106 [inline]
> wait_for_common kernel/sched/completion.c:117 [inline]
> wait_for_completion+0x174/0x270 kernel/sched/completion.c:138
> vhost_work_dev_flush.part.0+0xbb/0xf0 drivers/vhost/vhost.c:243
> vhost_work_dev_flush drivers/vhost/vhost.c:238 [inline]
> vhost_poll_flush+0x5e/0x80 drivers/vhost/vhost.c:252
> vhost_vsock_flush drivers/vhost/vsock.c:710 [inline]
> vhost_vsock_dev_release+0x1be/0x4b0 drivers/vhost/vsock.c:757
> __fput+0x286/0x9f0 fs/file_table.c:311
> task_work_run+0xdd/0x1a0 kernel/task_work.c:164
> exit_task_work include/linux/task_work.h:32 [inline]
> do_exit+0xb29/0x2a30 kernel/exit.c:806
> do_group_exit+0xd2/0x2f0 kernel/exit.c:935
> __do_sys_exit_group kernel/exit.c:946 [inline]
> __se_sys_exit_group kernel/exit.c:944 [inline]
> __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:944
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fbf04b83b89
> RSP: 002b:00007fff5bc9ca18 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 00007fbf04bf8330 RCX: 00007fbf04b83b89
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 00007fff5bc9cc08
> R10: 00007fff5bc9cc08 R11: 0000000000000246 R12: 00007fbf04bf8330
> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
> </TASK>
>
> Showing all locks held in the system:
> 1 lock held by khungtaskd/26:
> #0: ffffffff8bb83c20 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6460
> 2 locks held by getty/3275:
> #0: ffff88807f0db098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:244
> #1: ffffc90002b662e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xcf0/0x1230 drivers/tty/n_tty.c:2077
> 1 lock held by vhost-3632/3633:
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 26 Comm: khungtaskd Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
> nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111
> nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
> trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
> check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
> watchdog+0xc1d/0xf50 kernel/hung_task.c:369
> kthread+0x2e9/0x3a0 kernel/kthread.c:377
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> </TASK>
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1
> CPU: 1 PID: 3633 Comm: vhost-3632 Not tainted 5.17.0-rc3-syzkaller-00029-ge6251ab4551f #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:check_kcov_mode kernel/kcov.c:166 [inline]
> RIP: 0010:__sanitizer_cov_trace_pc+0xd/0x60 kernel/kcov.c:200
> Code: 00 00 e9 c6 41 66 02 66 0f 1f 44 00 00 48 8b be b0 01 00 00 e8 b4 ff ff ff 31 c0 c3 90 65 8b 05 29 f7 89 7e 89 c1 48 8b 34 24 <81> e1 00 01 00 00 65 48 8b 14 25 00 70 02 00 a9 00 01 ff 00 74 0e
> RSP: 0018:ffffc90000cd7c78 EFLAGS: 00000246
> RAX: 0000000080000000 RBX: ffff888079ca8a80 RCX: 0000000080000000
> RDX: 0000000000000000 RSI: ffffffff86d3f8fb RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: ffffc90000cd7c77
> R10: ffffffff86d3f8ed R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffdf716a3b8 CR3: 00000000235b6000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340
> vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366
> vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104
> vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372
> kthread+0x2e9/0x3a0 kernel/kthread.c:377
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> </TASK>
> ----------------
> Code disassembly (best guess):
> 0: 00 00 add %al,(%rax)
> 2: e9 c6 41 66 02 jmpq 0x26641cd
> 7: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
> d: 48 8b be b0 01 00 00 mov 0x1b0(%rsi),%rdi
> 14: e8 b4 ff ff ff callq 0xffffffcd
> 19: 31 c0 xor %eax,%eax
> 1b: c3 retq
> 1c: 90 nop
> 1d: 65 8b 05 29 f7 89 7e mov %gs:0x7e89f729(%rip),%eax # 0x7e89f74d
> 24: 89 c1 mov %eax,%ecx
> 26: 48 8b 34 24 mov (%rsp),%rsi
> * 2a: 81 e1 00 01 00 00 and $0x100,%ecx <-- trapping instruction
> 30: 65 48 8b 14 25 00 70 mov %gs:0x27000,%rdx
> 37: 02 00
> 39: a9 00 01 ff 00 test $0xff0100,%eax
> 3e: 74 0e je 0x4e
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
From 4951112bf98d3e10d3e9557986e5ca5419ca738f Mon Sep 17 00:00:00 2001
From: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Date: Mon, 21 Feb 2022 11:07:49 +0100
Subject: [PATCH] vhost/vsock: don't check owner in vhost_vsock_stop() while
releasing
vhost_vsock_stop() calls vhost_dev_check_owner() to check the device
ownership. It expects current->mm to be valid.
vhost_vsock_stop() is also called by vhost_vsock_dev_release() when
the user has not done close(), so when we are in do_exit(). In this
case current->mm is invalid and we're releasing the device, so we
should clean it anyway.
Let's check the owner only when vhost_vsock_stop() is called
by an ioctl.
Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: syzbot+1e3ea63db39f2b4440e0@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---
drivers/vhost/vsock.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index d6ca1c7ad513..f00d2dfd72b7 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -629,16 +629,18 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
return ret;
}
-static int vhost_vsock_stop(struct vhost_vsock *vsock)
+static int vhost_vsock_stop(struct vhost_vsock *vsock, bool check_owner)
{
size_t i;
int ret;
mutex_lock(&vsock->dev.mutex);
- ret = vhost_dev_check_owner(&vsock->dev);
- if (ret)
- goto err;
+ if (check_owner) {
+ ret = vhost_dev_check_owner(&vsock->dev);
+ if (ret)
+ goto err;
+ }
for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
struct vhost_virtqueue *vq = &vsock->vqs[i];
@@ -753,7 +755,7 @@ static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
* inefficient. Room for improvement here. */
vsock_for_each_connected_socket(vhost_vsock_reset_orphans);
- vhost_vsock_stop(vsock);
+ vhost_vsock_stop(vsock, false);
vhost_vsock_flush(vsock);
vhost_dev_stop(&vsock->dev);
@@ -868,7 +870,7 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
if (start)
return vhost_vsock_start(vsock);
else
- return vhost_vsock_stop(vsock);
+ return vhost_vsock_stop(vsock, true);
case VHOST_GET_FEATURES:
features = VHOST_VSOCK_FEATURES;
if (copy_to_user(argp, &features, sizeof(features)))
--
2.35.1