Tejun Heo 1edfe4ea16 kernfs: Fix spurious lockdep warning in kernfs_find_and_get_node_by_id() ... c25491747b ("kernfs: Add KERNFS_REMOVING flags") made kernfs_find_and_get_node_by_id() test kernfs_active() instead of KERNFS_ACTIVATED. kernfs_find_and_get_by_id() is called without holding the kernfs_rwsem triggering the following lockdep warning. WARNING: CPU: 1 PID: 6191 at fs/kernfs/dir.c:36 kernfs_active+0xe8/0x120 fs/kernfs/dir.c:38 Modules linked in: CPU: 1 PID: 6191 Comm: syz-executor.1 Not tainted 6.0.0-syzkaller-09413-g4899a36f91a9 #0 Hardware name: linux,dummy-virt (DT) pstate: 10000005 (nzcV daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : kernfs_active+0xe8/0x120 fs/kernfs/dir.c:36 lr : lock_is_held include/linux/lockdep.h:283 [inline] lr : kernfs_active+0x94/0x120 fs/kernfs/dir.c:36 sp : ffff8000182c7a00 x29: ffff8000182c7a00 x28: 0000000000000002 x27: 0000000000000001 x26: ffff00000ee1f6a8 x25: 1fffe00001dc3ed5 x24: 0000000000000000 x23: ffff80000ca1fba0 x22: ffff8000089efcb0 x21: 0000000000000001 x20: ffff0000091181d0 x19: ffff0000091181d0 x18: ffff00006a9e6b88 x17: 0000000000000000 x16: 0000000000000000 x15: ffff00006a9e6bc4 x14: 1ffff00003058f0e x13: 1fffe0000258c816 x12: ffff700003058f39 x11: 1ffff00003058f38 x10: ffff700003058f38 x9 : dfff800000000000 x8 : ffff80000e482f20 x7 : ffff0000091d8058 x6 : ffff80000e482c60 x5 : ffff000009402ee8 x4 : 1ffff00001bd1f46 x3 : 1fffe0000258c6d1 x2 : 0000000000000003 x1 : 00000000000000c0 x0 : 0000000000000000 Call trace: kernfs_active+0xe8/0x120 fs/kernfs/dir.c:38 kernfs_find_and_get_node_by_id+0x6c/0x140 fs/kernfs/dir.c:708 __kernfs_fh_to_dentry fs/kernfs/mount.c:102 [inline] kernfs_fh_to_dentry+0x88/0x1fc fs/kernfs/mount.c:128 exportfs_decode_fh_raw+0x104/0x560 fs/exportfs/expfs.c:435 exportfs_decode_fh+0x10/0x5c fs/exportfs/expfs.c:575 do_handle_to_path fs/fhandle.c:152 [inline] handle_to_path fs/fhandle.c:207 [inline] do_handle_open+0x2a4/0x7b0 fs/fhandle.c:223 __do_compat_sys_open_by_handle_at fs/fhandle.c:277 [inline] __se_compat_sys_open_by_handle_at fs/fhandle.c:274 [inline] __arm64_compat_sys_open_by_handle_at+0x6c/0x9c fs/fhandle.c:274 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x6c/0x260 arch/arm64/kernel/syscall.c:52 el0_svc_common.constprop.0+0xc4/0x254 arch/arm64/kernel/syscall.c:142 do_el0_svc_compat+0x40/0x70 arch/arm64/kernel/syscall.c:212 el0_svc_compat+0x54/0x140 arch/arm64/kernel/entry-common.c:772 el0t_32_sync_handler+0x90/0x140 arch/arm64/kernel/entry-common.c:782 el0t_32_sync+0x190/0x194 arch/arm64/kernel/entry.S:586 irq event stamp: 232 hardirqs last enabled at (231): [<ffff8000081edf70>] raw_spin_rq_unlock_irq kernel/sched/sched.h:1367 [inline] hardirqs last enabled at (231): [<ffff8000081edf70>] finish_lock_switch kernel/sched/core.c:4943 [inline] hardirqs last enabled at (231): [<ffff8000081edf70>] finish_task_switch.isra.0+0x200/0x880 kernel/sched/core.c:5061 hardirqs last disabled at (232): [<ffff80000c888bb4>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:404 softirqs last enabled at (228): [<ffff800008010938>] _stext+0x938/0xf58 softirqs last disabled at (207): [<ffff800008019380>] ____do_softirq+0x10/0x20 arch/arm64/kernel/irq.c:79 ---[ end trace 0000000000000000 ]--- The lockdep warning in kernfs_active() is there to ensure that the activated state stays stable for the caller. For kernfs_find_and_get_node_by_id(), all that's needed is ensuring that a node which has never been activated can't be looked up and guaranteeing lookup success when the caller knows the node to be active, both of which can be achieved by testing the active count without holding the kernfs_rwsem. Fix the spurious warning by introducing __kernfs_active() which doesn't have the lockdep annotation. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: syzbot+590ce62b128e79cf0a35@syzkaller.appspotmail.com Fixes: c25491747b ("kernfs: Add KERNFS_REMOVING flags") Cc: Amir Goldstein <amir73il@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Link: https://lore.kernel.org/r/Y0SwqBsZ9BMmZv6x@slm.duckdns.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-11-10 19:03:42 +01:00
..
dir.c	kernfs: Fix spurious lockdep warning in kernfs_find_and_get_node_by_id()	2022-11-10 19:03:42 +01:00
file.c	kernfs: Skip kernfs_drain_open_files() more aggressively	2022-09-01 18:08:44 +02:00
inode.c	kernfs: switch global kernfs_rwsem lock to per-fs lock	2021-11-24 13:55:16 +01:00
Kconfig	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
kernfs-internal.h	kernfs: Skip kernfs_drain_open_files() more aggressively	2022-09-01 18:08:44 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
mount.c	kernfs: Replace global kernfs_open_file_mutex with hashed mutexes.	2022-06-27 16:46:15 +02:00
symlink.c	kernfs: switch global kernfs_rwsem lock to per-fs lock	2021-11-24 13:55:16 +01:00