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.1.294:8828 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.1.294       state:D stack:23808 pid:8828  tgid:8827  ppid:5828   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+0x258/0x550 fs/f2fs/file.c:2284
 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: 0033:0x7f6582b75b59
RSP: 002b:00007f65825ff048 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6582d05f60 RCX: 00007f6582b75b59
RDX: 0000000020000140 RSI: 000000008004587d RDI: 0000000000000005
RBP: 00007f6582be4e5d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f6582d05f60 R15: 00007fff126c76c8
 </TASK>
INFO: task syz.1.294:8849 blocked for more than 144 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.1.294       state:D stack:26464 pid:8849  tgid:8827  ppid:5828   flags:0x00000004
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_preempt_disabled+0x13/0x30 kernel/sched/core.c:6678
 rwsem_down_write_slowpath+0xeeb/0x13b0 kernel/locking/rwsem.c:1178
 __down_write_common kernel/locking/rwsem.c:1306 [inline]
 __down_write kernel/locking/rwsem.c:1315 [inline]
 down_write+0x1d7/0x220 kernel/locking/rwsem.c:1580
 vfs_cmd_reconfigure fs/fsopen.c:262 [inline]
 vfs_fsconfig_locked fs/fsopen.c:292 [inline]
 __do_sys_fsconfig fs/fsopen.c:473 [inline]
 __se_sys_fsconfig+0xb64/0xf80 fs/fsopen.c:345
 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: 0033:0x7f6582b75b59
RSP: 002b:00007f65825de048 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 00007f6582d06038 RCX: 00007f6582b75b59
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000006
RBP: 00007f6582be4e5d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f6582d06038 R15: 00007fff126c76c8
 </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/u8:5/144:
2 locks held by getty/4844:
 #0: ffff88802afe40a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900031332f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2211
2 locks held by syz.1.294/8828:
 #0: ffff88801fb32420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
 #1: ffff88801fb320e0 (&type->s_umount_key#53){++++}-{3:3}, at: f2fs_do_shutdown+0x250/0x550 fs/f2fs/file.c:2283
2 locks held by syz.1.294/8849:
 #0: ffff88807eccac70 (&fc->uapi_mutex){+.+.}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:471 [inline]
 #0: ffff88807eccac70 (&fc->uapi_mutex){+.+.}-{3:3}, at: __se_sys_fsconfig+0x9a7/0xf80 fs/fsopen.c:345
 #1: ffff88801fb320e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_cmd_reconfigure fs/fsopen.c:262 [inline]
 #1: ffff88801fb320e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_fsconfig_locked fs/fsopen.c:292 [inline]
 #1: ffff88801fb320e0 (&type->s_umount_key#53){++++}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:473 [inline]
 #1: ffff88801fb320e0 (&type->s_umount_key#53){++++}-{3:3}, at: __se_sys_fsconfig+0xb64/0xf80 fs/fsopen.c:345
2 locks held by syz.4.517/10408:
 #0: ffff88802a168420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
 #1: ffff88802a1680e0 (&type->s_umount_key#53){++++}-{3:3}, at: f2fs_do_shutdown+0x250/0x550 fs/f2fs/file.c:2283
2 locks held by syz.4.517/10432:
 #0: ffff88801e248470 (&fc->uapi_mutex){+.+.}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:471 [inline]
 #0: ffff88801e248470 (&fc->uapi_mutex){+.+.}-{3:3}, at: __se_sys_fsconfig+0x9a7/0xf80 fs/fsopen.c:345
 #1: ffff88802a1680e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_cmd_reconfigure fs/fsopen.c:262 [inline]
 #1: ffff88802a1680e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_fsconfig_locked fs/fsopen.c:292 [inline]
 #1: ffff88802a1680e0 (&type->s_umount_key#53){++++}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:473 [inline]
 #1: ffff88802a1680e0 (&type->s_umount_key#53){++++}-{3:3}, at: __se_sys_fsconfig+0xb64/0xf80 fs/fsopen.c:345
2 locks held by syz.2.560/10729:
 #0: ffff88807866e420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:559
 #1: ffff88807866e0e0 (&type->s_umount_key#53){++++}-{3:3}, at: f2fs_do_shutdown+0x250/0x550 fs/f2fs/file.c:2283
2 locks held by syz.2.560/10730:
 #0: ffff88801cfb5870 (&fc->uapi_mutex){+.+.}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:471 [inline]
 #0: ffff88801cfb5870 (&fc->uapi_mutex){+.+.}-{3:3}, at: __se_sys_fsconfig+0x9a7/0xf80 fs/fsopen.c:345
 #1: ffff88807866e0e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_cmd_reconfigure fs/fsopen.c:262 [inline]
 #1: ffff88807866e0e0 (&type->s_umount_key#53){++++}-{3:3}, at: vfs_fsconfig_locked fs/fsopen.c:292 [inline]
 #1: ffff88807866e0e0 (&type->s_umount_key#53){++++}-{3:3}, at: __do_sys_fsconfig fs/fsopen.c:473 [inline]
 #1: ffff88807866e0e0 (&type->s_umount_key#53){++++}-{3:3}, at: __se_sys_fsconfig+0xb64/0xf80 fs/fsopen.c:345
2 locks held by syz.3.637/11108:
2 locks held by syz.0.640/11110:
2 locks held by syz.2.643/11116:

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

NMI backtrace for cpu 0
CPU: 0 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 12 Comm: kworker/u8:1 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:get_current arch/x86/include/asm/current.h:49 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x70 kernel/kcov.c:206
Code: 8b 3d 4c 70 4a 0c 48 89 de 5b e9 73 7c 57 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0c 25 40 d5 03 00 65 8b 15 70 92 70 7e f7 c2 00 01 ff 00
RSP: 0018:ffffc90000117790 EFLAGS: 00000297
RAX: ffffffff8b03874a RBX: 0000000000000008 RCX: ffff8880172bda00
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000002
RBP: 0000000000000014 R08: ffffffff8b03873b R09: 1ffffffff1f5d135
R10: dffffc0000000000 R11: fffffbfff1f5d136 R12: dffffc0000000000
R13: 0000000000000008 R14: ffff88807e0c30d0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1c7a489000 CR3: 000000001f196000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 ieee80211_sta_get_rates+0x20a/0x660 net/mac80211/util.c:1540
 ieee80211_update_sta_info net/mac80211/ibss.c:989 [inline]
 ieee80211_rx_bss_info net/mac80211/ibss.c:1098 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1579 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x11e1/0x2d70 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=14b2bea1980000
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=146ecebd980000