[v5.15] INFO: task hung in do_user_addr_fault

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29e53a5b1c4f Linux 5.15.194
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=130ea92f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=07cdd6021326bc8033cd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=110aaee2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16379092580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0eeaf49a514b/disk-29e53a5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0d94b4e7dfb6/vmlinux-29e53a5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/807fd9b16ada/bzImage-29e53a5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+07cdd6...@syzkaller.appspotmail.com

INFO: task syz-execprog:4228 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-execprog state:D stack:25664 pid: 4228 ppid: 4219 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
rwsem_down_read_slowpath+0x528/0x990 kernel/locking/rwsem.c:1055
__down_read_common kernel/locking/rwsem.c:1239 [inline]
__down_read kernel/locking/rwsem.c:1252 [inline]
down_read+0x96/0x2e0 kernel/locking/rwsem.c:1500
mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117
do_user_addr_fault+0xc35/0xc80 arch/x86/mm/fault.c:1308
handle_page_fault arch/x86/mm/fault.c:1445 [inline]
exc_page_fault+0x60/0x100 arch/x86/mm/fault.c:1501
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x427c87
RSP: 002b:000000c001b07e38 EFLAGS: 00010246
RAX: 000000c003020140 RBX: 000000c000fece10 RCX: 00000000000000a8
RDX: 00007f064c67b7e8 RSI: 000000c000065250 RDI: 00007f064c6cb560
RBP: 000000c001b07e70 R08: 000000000000000a R09: 0000000002033330
R10: 00000000000000a8 R11: 000000c003020140 R12: 0000000000000001
R13: 0000000000000001 R14: 000000c001517dc0 R15: 0000000000000001
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c11c660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by udevd/3560:
#0: ffffffff8c1a67f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
#0: ffffffff8c1a67f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
#0: ffffffff8c1a67f0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x21f/0x1380 kernel/fork.c:1518
#1: ffff88807cb38128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88807cb38128 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
#1: ffff88807cb38128 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#1: ffff88807cb38128 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x238/0x1380 kernel/fork.c:1518
2 locks held by getty/3949:
#0: ffff88814ce8d098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900025e62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
1 lock held by syz-execprog/4220:
#0: ffff888079b8b228 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff888079b8b228 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x15d/0x2b0 mm/util.c:549
1 lock held by syz-execprog/4228:
#0: ffff888079b8b228 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117
1 lock held by syz-executor/4229:
#0: ffff88801edd7828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88801edd7828 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x15d/0x2b0 mm/util.c:549
1 lock held by udevd/4348:
#0: ffff88802b662b28 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88802b662b28 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949

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

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:729


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