* Re: [syzbot] [bcachefs?] possible deadlock in pcpu_alloc_noprof
[not found] <66f97d9a.050a0220.6bad9.001d.GAE@google.com>
@ 2025-05-29 9:09 ` syzbot
0 siblings, 0 replies; only message in thread
From: syzbot @ 2025-05-29 9:09 UTC (permalink / raw)
To: axboe, cl, dennis, kent.overstreet, linux-bcachefs, linux-block,
linux-kernel, linux-mm, mhocko, mmpgouride, syzkaller-bugs, tj,
vbabka
syzbot has found a reproducer for the following issue on:
HEAD commit: 90b83efa6701 Merge tag 'bpf-next-6.16' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=145b4ed4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fbd871027e10b130
dashboard link: https://syzkaller.appspot.com/bug?extid=fe63f377148a6371a9db
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=166807f4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=125b4ed4580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7b23158542c6/disk-90b83efa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fe77cd0d7150/vmlinux-90b83efa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fdddbd2ed303/bzImage-90b83efa.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fe63f377148a6371a9db@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
6.15.0-syzkaller-07774-g90b83efa6701 #0 Not tainted
------------------------------------------------------
syz-executor398/5854 is trying to acquire lock:
ffffffff8e52d3a8 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4a/0x1470 mm/percpu.c:1782
but task is already holding lock:
ffff88814333d8b0 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&q->q_usage_counter(io)#58){++++}-{0:0}:
blk_alloc_queue+0x619/0x760 block/blk-core.c:461
blk_mq_alloc_queue+0x175/0x290 block/blk-mq.c:4396
__blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4443
nbd_dev_add+0x4a0/0xbc0 drivers/block/nbd.c:1933
nbd_init+0x181/0x320 drivers/block/nbd.c:2670
do_one_initcall+0x120/0x6e0 init/main.c:1257
do_initcall_level init/main.c:1319 [inline]
do_initcalls init/main.c:1335 [inline]
do_basic_setup init/main.c:1354 [inline]
kernel_init_freeable+0x5c2/0x900 init/main.c:1567
kernel_init+0x1c/0x2b0 init/main.c:1457
ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
-> #1 (fs_reclaim){+.+.}-{0:0}:
__fs_reclaim_acquire mm/page_alloc.c:4056 [inline]
fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4070
might_alloc include/linux/sched/mm.h:318 [inline]
prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4738
__alloc_frozen_pages_noprof+0x18b/0x23f0 mm/page_alloc.c:4959
__alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:5004
__alloc_pages_node_noprof include/linux/gfp.h:284 [inline]
alloc_pages_node_noprof include/linux/gfp.h:311 [inline]
pcpu_alloc_pages mm/percpu-vm.c:95 [inline]
pcpu_populate_chunk+0x110/0xb00 mm/percpu-vm.c:285
pcpu_alloc_noprof+0x86a/0x1470 mm/percpu.c:1870
xt_percpu_counter_alloc+0x13e/0x1b0 net/netfilter/x_tables.c:1931
find_check_entry.constprop.0+0xbc/0x9b0 net/ipv4/netfilter/ip_tables.c:526
translate_table+0xc98/0x1720 net/ipv4/netfilter/ip_tables.c:716
ipt_register_table+0x102/0x430 net/ipv4/netfilter/ip_tables.c:1742
iptable_raw_table_init+0x63/0x90 net/ipv4/netfilter/iptable_raw.c:49
xt_find_table_lock+0x2e1/0x520 net/netfilter/x_tables.c:1260
xt_request_find_table_lock+0x28/0xf0 net/netfilter/x_tables.c:1285
get_info+0x190/0x610 net/ipv4/netfilter/ip_tables.c:963
do_ipt_get_ctl+0x169/0xa10 net/ipv4/netfilter/ip_tables.c:1659
nf_getsockopt+0x7c/0xe0 net/netfilter/nf_sockopt.c:116
ip_getsockopt+0x18c/0x1e0 net/ipv4/ip_sockglue.c:1777
tcp_getsockopt+0x9e/0x100 net/ipv4/tcp.c:4760
do_sock_getsockopt+0x3ff/0x800 net/socket.c:2357
__sys_getsockopt+0x123/0x1b0 net/socket.c:2386
__do_sys_getsockopt net/socket.c:2393 [inline]
__se_sys_getsockopt net/socket.c:2390 [inline]
__x64_sys_getsockopt+0xbd/0x160 net/socket.c:2390
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (pcpu_alloc_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
lock_acquire kernel/locking/lockdep.c:5871 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
pcpu_alloc_noprof+0xb4a/0x1470 mm/percpu.c:1782
blk_stat_alloc_callback+0xc8/0x280 block/blk-stat.c:116
wbt_init+0xac/0x540 block/blk-wbt.c:903
queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603
queue_attr_store+0x276/0x320 block/blk-sysfs.c:805
sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x6c7/0x1150 fs/read_write.c:686
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
pcpu_alloc_mutex --> fs_reclaim --> &q->q_usage_counter(io)#58
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&q->q_usage_counter(io)#58);
lock(fs_reclaim);
lock(&q->q_usage_counter(io)#58);
lock(pcpu_alloc_mutex);
*** DEADLOCK ***
5 locks held by syz-executor398/5854:
#0: ffff8880316b8428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
#1: ffff88802a508088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
#2: ffff888147e9ac38 (kn->active#57){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326
#3: ffff88814333d8b0 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
#4: ffff88814333d8e8 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205
stack backtrace:
CPU: 1 UID: 0 PID: 5854 Comm: syz-executor398 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046
check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178
check_prev_add kernel/locking/lockdep.c:3168 [inline]
check_prevs_add kernel/locking/lockdep.c:3287 [inline]
validate_chain kernel/locking/lockdep.c:3911 [inline]
__lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
lock_acquire kernel/locking/lockdep.c:5871 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
__mutex_lock_common kernel/locking/mutex.c:601 [inline]
__mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746
pcpu_alloc_noprof+0xb4a/0x1470 mm/percpu.c:1782
blk_stat_alloc_callback+0xc8/0x280 block/blk-stat.c:116
wbt_init+0xac/0x540 block/blk-wbt.c:903
queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603
queue_attr_store+0x276/0x320 block/blk-sysfs.c:805
sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145
kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x6c7/0x1150 fs/read_write.c:686
ksys_write+0x12a/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f18df4b0e49
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 1d 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc61925058 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f18df4b0e49
RDX: 0000000000000801 RSI: 0000200000000240 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffc61925090 R14: 00007ffc619250d0 R15: 0000000000000000
</TASK>
---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
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