Re: [syzbot] [f2fs?] KASAN: null-ptr-deref Write in f2fs_stop_gc_thread

[syzbot <syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in f2fs_stop_gc_thread

INFO: task syz.3.52:6722 blocked for more than 143 seconds.
      Not tainted 6.10.0-syzkaller-11185-g2c9b3512402e-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.52        state:D stack:26464 pid:6722  tgid:6680  ppid:5910   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5188 [inline]
 __schedule+0x17ae/0x4a10 kernel/sched/core.c:6529
 __schedule_loop kernel/sched/core.c:6606 [inline]
 schedule+0x14b/0x320 kernel/sched/core.c:6621
 schedule_timeout+0xb0/0x310 kernel/time/timer.c:2557
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x355/0x620 kernel/sched/completion.c:148
 kthread_stop+0x19e/0x630 kernel/kthread.c:710
 f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210
 f2fs_do_shutdown+0x250/0x550 fs/f2fs/file.c:2285
 f2fs_ioc_shutdown fs/f2fs/file.c:2327 [inline]
 __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4327
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f24e1d75b59
RSP: 002b:00007f24e17ff048 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f24e1f06038 RCX: 00007f24e1d75b59
RDX: 0000000020000140 RSI: 000000008004587d RDI: 0000000000000005
RBP: 00007f24e1de4e5d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f24e1f06038 R15: 00007ffdd92ac938
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8e336e60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:327 [inline]
 #0: ffffffff8e336e60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:839 [inline]
 #0: ffffffff8e336e60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6620
3 locks held by kworker/u8:2/35:
5 locks held by kworker/u8:8/1113:
2 locks held by getty/4843:
 #0: ffff88802aa340a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2211
1 lock held by syz.3.52/6722:
 #0: ffff88807c804420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
1 lock held by syz.4.98/7235:
 #0: ffff88807d5a2420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
1 lock held by syz.1.241/8092:
 #0: ffff88802c114420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
1 lock held by syz.2.274/8239:
 #0: ffff88807b344420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
1 lock held by syz.4.422/8825:
2 locks held by syz.1.423/8831:

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

NMI backtrace for cpu 1
CPU: 1 PID: 30 Comm: khungtaskd Not tainted 6.10.0-syzkaller-11185-g2c9b3512402e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
 watchdog+0xfde/0x1020 kernel/hung_task.c:379
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 35 Comm: kworker/u8:2 Not tainted 6.10.0-syzkaller-11185-g2c9b3512402e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x90 kernel/kcov.c:303
Code: 10 48 89 74 0a 18 4c 89 44 0a 20 c3 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 4c 8b 04 24 65 48 8b 14 25 40 d5 03 00 65 8b 05 30 8e
RSP: 0018:ffffc90000ab7838 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 000000000000004c RCX: ffff88801b293c00
RDX: 0000000000000000 RSI: 000000000000004c RDI: 0000000000000024
RBP: ffffc90000ab7ae8 R08: 0000000000000005 R09: ffffffff8af5c942
R10: 0000000000000006 R11: ffff88801b293c00 R12: dffffc0000000000
R13: ffff8880428fccc0 R14: ffff88802b095e50 R15: 1ffff92000156f20
FS:  0000000000000000(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f834aa06000 CR3: 000000000e134000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1572 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x3f3/0x2d70 net/mac80211/ibss.c:1606
 ieee80211_iface_process_skb net/mac80211/iface.c:1588 [inline]
 ieee80211_iface_work+0x8a5/0xf20 net/mac80211/iface.c:1642
 cfg80211_wiphy_work+0x2db/0x490 net/wireless/core.c:440
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd40 kernel/workqueue.c:3390
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


Tested on:

commit:         2c9b3512 Merge tag 'for-linus' of git://git.kernel.org..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=101229f1980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f4925140c45a2a50
dashboard link: https://syzkaller.appspot.com/bug?extid=1a8e2b31f2ac9bd3d148
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1204adad980000