[syzbot] [fs?] possible deadlock in start_creating (2)

From: syzbot
Date: Mon Jan 20 2025 - 11:50:43 EST

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Hello,

syzbot found the following issue on:

HEAD commit: be548645527a Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11fbb1df980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ad08f7f48e13abcd
dashboard link: https://syzkaller.appspot.com/bug?extid=674b1c12641a6992f1d5
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68edb33a6611/disk-be548645.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9c748ff58068/vmlinux-be548645.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6ae2859fc0e3/bzImage-be548645.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+674b1c12641a6992f1d5@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc6-syzkaller-00290-gbe548645527a #0 Not tainted
------------------------------------------------------
syz.7.2798/18466 is trying to acquire lock:
ffff8880621f6988 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: inode_lock include/linux/fs.h:818 [inline]
ffff8880621f6988 (&sb->s_type->i_mutex_key#3){++++}-{4:4}, at: start_creating.part.0+0xb0/0x3a0 fs/debugfs/inode.c:374

but task is already holding lock:
ffffffff8de395c8 (relay_channels_mutex){+.+.}-{4:4}, at: relay_open+0x324/0xa20 kernel/relay.c:515

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (relay_channels_mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:585 [inline]
__mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
relay_prepare_cpu+0x2c/0x300 kernel/relay.c:438
cpuhp_invoke_callback+0x3d0/0xa10 kernel/cpu.c:194
__cpuhp_invoke_callback_range+0x101/0x200 kernel/cpu.c:965
cpuhp_invoke_callback_range kernel/cpu.c:989 [inline]
cpuhp_up_callbacks kernel/cpu.c:1020 [inline]
_cpu_up+0x3fd/0x910 kernel/cpu.c:1690
cpu_up+0x1dc/0x240 kernel/cpu.c:1722
cpuhp_bringup_mask+0xdc/0x210 kernel/cpu.c:1788
cpuhp_bringup_cpus_parallel kernel/cpu.c:1878 [inline]
bringup_nonboot_cpus+0x176/0x1c0 kernel/cpu.c:1892
smp_init+0x34/0x160 kernel/smp.c:1009
kernel_init_freeable+0x3ad/0x8b0 init/main.c:1569
kernel_init+0x1c/0x2b0 init/main.c:1466
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #1 (cpu_hotplug_lock){++++}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
cpus_read_lock+0x42/0x160 kernel/cpu.c:490
acomp_ctx_get_cpu mm/zswap.c:886 [inline]
zswap_compress mm/zswap.c:908 [inline]
zswap_store_page mm/zswap.c:1439 [inline]
zswap_store+0x8f8/0x25f0 mm/zswap.c:1546
swap_writepage+0x3b6/0x1120 mm/page_io.c:279
shmem_writepage+0xf7b/0x1490 mm/shmem.c:1579
pageout+0x3b2/0xaa0 mm/vmscan.c:696
shrink_folio_list+0x3025/0x42d0 mm/vmscan.c:1374
evict_folios+0x6e3/0x19c0 mm/vmscan.c:4600
try_to_shrink_lruvec+0x61e/0xa80 mm/vmscan.c:4796
lru_gen_shrink_lruvec mm/vmscan.c:4945 [inline]
shrink_lruvec+0x313/0x2ba0 mm/vmscan.c:5700
shrink_node_memcgs mm/vmscan.c:5936 [inline]
shrink_node mm/vmscan.c:5977 [inline]
shrink_node+0x105e/0x3f20 mm/vmscan.c:5955
shrink_zones mm/vmscan.c:6222 [inline]
do_try_to_free_pages+0x35f/0x1a30 mm/vmscan.c:6284
try_to_free_mem_cgroup_pages+0x31a/0x7a0 mm/vmscan.c:6616
try_charge_memcg+0x356/0xaf0 mm/memcontrol.c:2238
obj_cgroup_charge_pages mm/memcontrol.c:2646 [inline]
obj_cgroup_charge+0x179/0x4d0 mm/memcontrol.c:2937
__memcg_slab_post_alloc_hook+0x1b6/0x9b0 mm/memcontrol.c:2998
memcg_slab_post_alloc_hook mm/slub.c:2152 [inline]
slab_post_alloc_hook mm/slub.c:4129 [inline]
slab_alloc_node mm/slub.c:4168 [inline]
kmem_cache_alloc_lru_noprof+0x30d/0x3b0 mm/slub.c:4187
alloc_inode+0xbf/0x230 fs/inode.c:338
new_inode_pseudo fs/inode.c:1174 [inline]
new_inode+0x22/0x210 fs/inode.c:1193
debugfs_get_inode fs/debugfs/inode.c:72 [inline]
__debugfs_create_file+0x11a/0x660 fs/debugfs/inode.c:433
debugfs_create_file_full+0x6d/0xa0 fs/debugfs/inode.c:462
kvm_create_vm_debugfs virt/kvm/kvm_main.c:1056 [inline]
kvm_create_vm virt/kvm/kvm_main.c:1193 [inline]
kvm_dev_ioctl_create_vm virt/kvm/kvm_main.c:5353 [inline]
kvm_dev_ioctl+0x16b7/0x1aa0 virt/kvm/kvm_main.c:5395
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl fs/ioctl.c:892 [inline]
__x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sb->s_type->i_mutex_key#3){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain kernel/locking/lockdep.c:3904 [inline]
__lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
down_write+0x93/0x200 kernel/locking/rwsem.c:1577
inode_lock include/linux/fs.h:818 [inline]
start_creating.part.0+0xb0/0x3a0 fs/debugfs/inode.c:374
start_creating fs/debugfs/inode.c:351 [inline]
__debugfs_create_file+0xa5/0x660 fs/debugfs/inode.c:423
debugfs_create_file_full+0x6d/0xa0 fs/debugfs/inode.c:462
relay_create_buf_file+0xf0/0x170 kernel/relay.c:360
relay_open_buf.part.0+0x760/0xb90 kernel/relay.c:389
relay_open_buf kernel/relay.c:536 [inline]
relay_open+0x5e2/0xa20 kernel/relay.c:517
do_blk_trace_setup+0x4b4/0xac0 kernel/trace/blktrace.c:590
__blk_trace_setup+0xd8/0x180 kernel/trace/blktrace.c:630
blk_trace_setup+0x47/0x70 kernel/trace/blktrace.c:648
sg_ioctl_common drivers/scsi/sg.c:1114 [inline]
sg_ioctl+0x7a3/0x26b0 drivers/scsi/sg.c:1156
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl fs/ioctl.c:892 [inline]
__x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&sb->s_type->i_mutex_key#3 --> cpu_hotplug_lock --> relay_channels_mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(relay_channels_mutex);
lock(cpu_hotplug_lock);
lock(relay_channels_mutex);
lock(&sb->s_type->i_mutex_key#3);

*** DEADLOCK ***

2 locks held by syz.7.2798/18466:
#0: ffff8881433b1ca8 (&q->debugfs_mutex){+.+.}-{4:4}, at: blk_trace_setup+0x33/0x70 kernel/trace/blktrace.c:647
#1: ffffffff8de395c8 (relay_channels_mutex){+.+.}-{4:4}, at: relay_open+0x324/0xa20 kernel/relay.c:515

stack backtrace:
CPU: 1 UID: 0 PID: 18466 Comm: syz.7.2798 Not tainted 6.13.0-rc6-syzkaller-00290-gbe548645527a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_circular_bug+0x41c/0x610 kernel/locking/lockdep.c:2074
check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
check_prev_add kernel/locking/lockdep.c:3161 [inline]
check_prevs_add kernel/locking/lockdep.c:3280 [inline]
validate_chain kernel/locking/lockdep.c:3904 [inline]
__lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
down_write+0x93/0x200 kernel/locking/rwsem.c:1577
inode_lock include/linux/fs.h:818 [inline]
start_creating.part.0+0xb0/0x3a0 fs/debugfs/inode.c:374
start_creating fs/debugfs/inode.c:351 [inline]
__debugfs_create_file+0xa5/0x660 fs/debugfs/inode.c:423
debugfs_create_file_full+0x6d/0xa0 fs/debugfs/inode.c:462
relay_create_buf_file+0xf0/0x170 kernel/relay.c:360
relay_open_buf.part.0+0x760/0xb90 kernel/relay.c:389
relay_open_buf kernel/relay.c:536 [inline]
relay_open+0x5e2/0xa20 kernel/relay.c:517
do_blk_trace_setup+0x4b4/0xac0 kernel/trace/blktrace.c:590
__blk_trace_setup+0xd8/0x180 kernel/trace/blktrace.c:630
blk_trace_setup+0x47/0x70 kernel/trace/blktrace.c:648
sg_ioctl_common drivers/scsi/sg.c:1114 [inline]
sg_ioctl+0x7a3/0x26b0 drivers/scsi/sg.c:1156
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl fs/ioctl.c:892 [inline]
__x64_sys_ioctl+0x190/0x200 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f596cf85d29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f596de83038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f596d176080 RCX: 00007f596cf85d29
RDX: 0000000000000038 RSI: 00000000c0481273 RDI: 0000000000000003
RBP: 00007f596d001b08 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f596d176080 R15: 00007ffc52cefc58
</TASK>

---
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Next message: syzbot: "[syzbot] [fs?] possible deadlock in v2_read_dquot"
Previous message: Andrew Lunn: "Re: [PATCH 2/3] net: stmmac: qcom-ethqos: Enable RX programmable swap on qcs615"
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