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definitions=main-2409270064 [Syzbot reported] WARNING: possible circular locking dependency detected 6.11.0-rc4-syzkaller-00019-gb311c1b497e5 #0 Not tainted ------------------------------------------------------ kswapd0/78 is trying to acquire lock: ffff88801b8d8930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline] ffff88801b8d8930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578 but task is already holding lock: ffffffff8ea2fd60 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6841 [inline] ffffffff8ea2fd60 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbb4/0x35a0 mm/vmscan.c:7223 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __fs_reclaim_acquire mm/page_alloc.c:3818 [inline] fs_reclaim_acquire+0x88/0x140 mm/page_alloc.c:3832 might_alloc include/linux/sched/mm.h:334 [inline] slab_pre_alloc_hook mm/slub.c:3939 [inline] slab_alloc_node mm/slub.c:4017 [inline] kmem_cache_alloc_noprof+0x3d/0x2a0 mm/slub.c:4044 inotify_new_watch fs/notify/inotify/inotify_user.c:599 [inline] inotify_update_watch fs/notify/inotify/inotify_user.c:647 [inline] __do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:786 [inline] __se_sys_inotify_add_watch+0x72e/0x1070 fs/notify/inotify/inotify_user.c:729 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 -> #0 (&group->mark_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3133 [inline] check_prevs_add kernel/locking/lockdep.c:3252 [inline] validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline] fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578 fsnotify_destroy_marks+0x14a/0x660 fs/notify/mark.c:934 fsnotify_inoderemove include/linux/fsnotify.h:264 [inline] dentry_unlink_inode+0x2e0/0x430 fs/dcache.c:403 __dentry_kill+0x20d/0x630 fs/dcache.c:610 shrink_kill+0xa9/0x2c0 fs/dcache.c:1055 shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1082 prune_dcache_sb+0x10f/0x180 fs/dcache.c:1163 super_cache_scan+0x34f/0x4b0 fs/super.c:221 do_shrink_slab+0x701/0x1160 mm/shrinker.c:435 shrink_slab+0x1093/0x14d0 mm/shrinker.c:662 shrink_one+0x43b/0x850 mm/vmscan.c:4815 shrink_many mm/vmscan.c:4876 [inline] lru_gen_shrink_node mm/vmscan.c:4954 [inline] shrink_node+0x3799/0x3de0 mm/vmscan.c:5934 kswapd_shrink_node mm/vmscan.c:6762 [inline] balance_pgdat mm/vmscan.c:6954 [inline] kswapd+0x1bcd/0x35a0 mm/vmscan.c:7223 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 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&group->mark_mutex); lock(fs_reclaim); lock(&group->mark_mutex); *** DEADLOCK *** [Analysis] The inotify_new_watch() call passes through GFP_KERNEL, use memalloc_nofs_save/ memalloc_nofs_restore to make sure we don't end up with the fs reclaim dependency. Reported-and-tested-by: syzbot+c679f13773f295d2da53@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c679f13773f295d2da53 Signed-off-by: Lizhi Xu --- fs/notify/inotify/inotify_user.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index c7e451d5bd51..70b77b6186a6 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -643,8 +643,13 @@ static int inotify_update_watch(struct fsnotify_group *group, struct inode *inod /* try to update and existing watch with the new arg */ ret = inotify_update_existing_watch(group, inode, arg); /* no mark present, try to add a new one */ - if (ret == -ENOENT) + if (ret == -ENOENT) { + unsigned int nofs_flag; + + nofs_flag = memalloc_nofs_save(); ret = inotify_new_watch(group, inode, arg); + memalloc_nofs_restore(nofs_flag); + } fsnotify_group_unlock(group); return ret;