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SubjectINFO: task hung in __ia32_sys_io_uring_enter
From
Hello,

syzbot found the following crash on:

HEAD commit: 8ee15f32 Merge tag 'dma-mapping-5.1-1' of git://git.infrad..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b2e69f200000
kernel config: https://syzkaller.appspot.com/x/.config?x=4fb64439e07a1ec0
dashboard link: https://syzkaller.appspot.com/bug?extid=96642d282922abc6ef90
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+96642d282922abc6ef90@syzkaller.appspotmail.com

INFO: task syz-executor.2:6936 blocked for more than 143 seconds.
Not tainted 5.1.0-rc4+ #64
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D27432 6936 7877 0x20020004
Call Trace:
context_switch kernel/sched/core.c:2877 [inline]
__schedule+0x817/0x1cc0 kernel/sched/core.c:3518
schedule+0x92/0x180 kernel/sched/core.c:3562
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3620
__mutex_lock_common kernel/locking/mutex.c:1002 [inline]
__mutex_lock+0x726/0x1310 kernel/locking/mutex.c:1072
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
__do_sys_io_uring_enter fs/io_uring.c:2674 [inline]
__se_sys_io_uring_enter fs/io_uring.c:2633 [inline]
__ia32_sys_io_uring_enter+0x67f/0xac0 fs/io_uring.c:2633
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fdf869
Code: Bad RIP value.
RSP: 002b:00000000f5ddb0cc EFLAGS: 00000296 ORIG_RAX: 00000000000001aa
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000009
RDX: 0000000000000006 RSI: 0000000000000002 RDI: 0000000020000180
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
INFO: task syz-executor.2:6941 blocked for more than 143 seconds.
Not tainted 5.1.0-rc4+ #64
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D30304 6941 7877 0x20020004
Call Trace:
context_switch kernel/sched/core.c:2877 [inline]
__schedule+0x817/0x1cc0 kernel/sched/core.c:3518
schedule+0x92/0x180 kernel/sched/core.c:3562
schedule_timeout+0x8ca/0xfd0 kernel/time/timer.c:1779
do_wait_for_common kernel/sched/completion.c:83 [inline]
__wait_for_common kernel/sched/completion.c:104 [inline]
wait_for_common kernel/sched/completion.c:115 [inline]
wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136
__io_uring_register+0xb6/0x1fd0 fs/io_uring.c:2925
__do_sys_io_uring_register fs/io_uring.c:2975 [inline]
__se_sys_io_uring_register fs/io_uring.c:2957 [inline]
__ia32_sys_io_uring_register+0x193/0x1f0 fs/io_uring.c:2957
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fdf869
Code: Bad RIP value.
RSP: 002b:00000000f5dba0cc EFLAGS: 00000296 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000001
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Showing all locks held in the system:
1 lock held by khungtaskd/1042:
#0: 000000000fd6a12d (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:5061
1 lock held by rsyslogd/7748:
#0: 00000000b7bd7c78 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:801
2 locks held by getty/7837:
#0: 000000002675dd1e (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 000000008bb68d6f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7838:
#0: 000000000272332d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 000000006c00cca5 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7839:
#0: 0000000083b27adb (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 00000000778dee56 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7840:
#0: 00000000919ed15e (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 00000000dc8f8c82 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7841:
#0: 00000000a69742ff (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 00000000cc818dd5 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7842:
#0: 0000000031f786e7 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 00000000c793de16 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by getty/7843:
#0: 00000000c09fbaf2 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
#1: 000000000915b78b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2156
2 locks held by kworker/u4:4/3512:
#0: 00000000c5d7093f (&rq->lock){-.-.}, at: idle_balance
kernel/sched/fair.c:10053 [inline]
#0: 00000000c5d7093f (&rq->lock){-.-.}, at:
pick_next_task_fair+0x1214/0x19a0 kernel/sched/fair.c:7062
#1: 000000000fd6a12d (rcu_read_lock){....}, at:
__update_idle_core+0x45/0x3f0 kernel/sched/fair.c:6059
1 lock held by syz-executor.2/6936:
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at: __do_sys_io_uring_enter
fs/io_uring.c:2674 [inline]
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at: __se_sys_io_uring_enter
fs/io_uring.c:2633 [inline]
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at:
__ia32_sys_io_uring_enter+0x67f/0xac0 fs/io_uring.c:2633
1 lock held by syz-executor.2/6941:
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at:
__do_sys_io_uring_register fs/io_uring.c:2974 [inline]
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at:
__se_sys_io_uring_register fs/io_uring.c:2957 [inline]
#0: 0000000020d6f30f (&ctx->uring_lock){+.+.}, at:
__ia32_sys_io_uring_register+0x182/0x1f0 fs/io_uring.c:2957

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1042 Comm: khungtaskd Not tainted 5.1.0-rc4+ #64
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1be/0x236 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
watchdog+0x9b7/0xec0 kernel/hung_task.c:288
kthread+0x357/0x430 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 0 to CPUs 1:


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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