=============================
WARNING: suspicious RCU usage
6.14.0-rc2-next-20250217-syzkaller #0 Not tainted
-----------------------------
fs/kernfs/mount.c:243 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
3 locks held by syz.0.678/8377:
#0: ffff88805db69c70 (&fc->uapi_mutex){+.+.}-{4:4}, at: __do_sys_fsconfig fs/fsopen.c:465 [inline]
#0: ffff88805db69c70 (&fc->uapi_mutex){+.+.}-{4:4}, at: __se_sys_fsconfig+0x9b2/0xf60 fs/fsopen.c:344
#1: ffff8880330500e0 (&type->s_umount_key#89){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
#1: ffff8880330500e0 (&type->s_umount_key#89){++++}-{4:4}, at: super_lock+0x196/0x400 fs/super.c:120
#2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline]
#2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223
stack backtrace:
CPU: 0 UID: 0 PID: 8377 Comm: syz.0.678 Not tainted 6.14.0-rc2-next-20250217-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
lockdep_rcu_suspicious+0x226/0x340 kernel/locking/lockdep.c:6847
kernfs_node_dentry+0x24b/0x2d0 fs/kernfs/mount.c:243
cgroup_do_get_tree+0x248/0x390 kernel/cgroup/cgroup.c:2233
cgroup_get_tree+0xbb/0x230 kernel/cgroup/cgroup.c:2272
vfs_get_tree+0x90/0x2b0 fs/super.c:1759
vfs_cmd_create+0xa0/0x1f0 fs/fsopen.c:225
__do_sys_fsconfig fs/fsopen.c:467 [inline]
__se_sys_fsconfig+0xa33/0xf60 fs/fsopen.c:344
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: 0033:0x7fa566f8cde9
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:00007fa567cfe038 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 00007fa5671a5fa0 RCX: 00007fa566f8cde9
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003
RBP: 00007fa56700e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa5671a5fa0 R15: 00007fffb50d5778
============================================
WARNING: possible recursive locking detected
6.14.0-rc2-next-20250217-syzkaller #0 Not tainted
--------------------------------------------
syz.0.678/8377 is trying to acquire lock:
ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_dop_revalidate+0xa2/0x5d0 fs/kernfs/dir.c:1178
but task is already holding lock:
ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline]
ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&root->kernfs_rwsem);
lock(&root->kernfs_rwsem);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by syz.0.678/8377:
#0: ffff88805db69c70 (&fc->uapi_mutex){+.+.}-{4:4}, at: __do_sys_fsconfig fs/fsopen.c:465 [inline]
#0: ffff88805db69c70 (&fc->uapi_mutex){+.+.}-{4:4}, at: __se_sys_fsconfig+0x9b2/0xf60 fs/fsopen.c:344
#1: ffff8880330500e0 (&type->s_umount_key#89){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
#1: ffff8880330500e0 (&type->s_umount_key#89){++++}-{4:4}, at: super_lock+0x196/0x400 fs/super.c:120
#2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline]
#2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223
stack backtrace:
CPU: 1 UID: 0 PID: 8377 Comm: syz.0.678 Not tainted 6.14.0-rc2-next-20250217-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3039
check_deadlock kernel/locking/lockdep.c:3091 [inline]
validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3893
__lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524
kernfs_dop_revalidate+0xa2/0x5d0 fs/kernfs/dir.c:1178
d_revalidate fs/namei.c:923 [inline]
lookup_dcache fs/namei.c:1651 [inline]
lookup_one_unlocked+0x23b/0x2d0 fs/namei.c:2972
lookup_one_positive_unlocked fs/namei.c:3003 [inline]
lookup_positive_unlocked+0x2b/0xb0 fs/namei.c:3043
kernfs_node_dentry+0x139/0x2d0 fs/kernfs/mount.c:244
cgroup_do_get_tree+0x248/0x390 kernel/cgroup/cgroup.c:2233
cgroup_get_tree+0xbb/0x230 kernel/cgroup/cgroup.c:2272
vfs_get_tree+0x90/0x2b0 fs/super.c:1759
vfs_cmd_create+0xa0/0x1f0 fs/fsopen.c:225
__do_sys_fsconfig fs/fsopen.c:467 [inline]
__se_sys_fsconfig+0xa33/0xf60 fs/fsopen.c:344
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: 0033:0x7fa566f8cde9
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:00007fa567cfe038 EFLAGS: 00000246 ORIG_RAX: 00000000000001af
RAX: ffffffffffffffda RBX: 00007fa5671a5fa0 RCX: 00007fa566f8cde9
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003
RBP: 00007fa56700e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa5671a5fa0 R15: 00007fffb50d5778