Direct reclaim from fanotify mark allocation context may try to evict inodes with evictable marks of the same group and hit this deadlock: [<0>] fsnotify_destroy_mark+0x1f/0x3a [<0>] fsnotify_destroy_marks+0x71/0xd9 [<0>] __destroy_inode+0x24/0x7e [<0>] destroy_inode+0x2c/0x67 [<0>] dispose_list+0x49/0x68 [<0>] prune_icache_sb+0x5b/0x79 [<0>] super_cache_scan+0x11c/0x16f [<0>] shrink_slab.constprop.0+0x23e/0x40f [<0>] shrink_node+0x218/0x3e7 [<0>] do_try_to_free_pages+0x12a/0x2d2 [<0>] try_to_free_pages+0x166/0x242 [<0>] __alloc_pages_slowpath.constprop.0+0x30c/0x903 [<0>] __alloc_pages+0xeb/0x1c7 [<0>] cache_grow_begin+0x6f/0x31e [<0>] fallback_alloc+0xe0/0x12d [<0>] ____cache_alloc_node+0x15a/0x17e [<0>] kmem_cache_alloc_trace+0xa1/0x143 [<0>] fanotify_add_mark+0xd5/0x2b2 [<0>] do_fanotify_mark+0x566/0x5eb [<0>] __x64_sys_fanotify_mark+0x21/0x24 [<0>] do_syscall_64+0x6d/0x80 [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xae Set the FSNOTIFY_GROUP_NOFS flag to prevent going into direct reclaim from allocations under fanotify group lock and use the safe group lock helpers. Suggested-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/20220321112310.vpr7oxro2xkz5llh@xxxxxxxxxx/ Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/notify/fanotify/fanotify_user.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 0b4beba95fa8..fe2534043c17 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -1035,10 +1035,10 @@ static int fanotify_remove_mark(struct fsnotify_group *group, __u32 removed; int destroy_mark; - mutex_lock(&group->mark_mutex); + fsnotify_group_lock(group); fsn_mark = fsnotify_find_mark(connp, group); if (!fsn_mark) { - mutex_unlock(&group->mark_mutex); + fsnotify_group_unlock(group); return -ENOENT; } @@ -1048,7 +1048,7 @@ static int fanotify_remove_mark(struct fsnotify_group *group, fsnotify_recalc_mask(fsn_mark->connector); if (destroy_mark) fsnotify_detach_mark(fsn_mark); - mutex_unlock(&group->mark_mutex); + fsnotify_group_unlock(group); if (destroy_mark) fsnotify_free_mark(fsn_mark); @@ -1200,13 +1200,13 @@ static int fanotify_add_mark(struct fsnotify_group *group, struct fsnotify_mark *fsn_mark; int ret; - mutex_lock(&group->mark_mutex); + fsnotify_group_lock(group); fsn_mark = fsnotify_find_mark(connp, group); if (!fsn_mark) { fsn_mark = fanotify_add_new_mark(group, connp, obj_type, flags, fsid); if (IS_ERR(fsn_mark)) { - mutex_unlock(&group->mark_mutex); + fsnotify_group_unlock(group); return PTR_ERR(fsn_mark); } } @@ -1232,7 +1232,7 @@ static int fanotify_add_mark(struct fsnotify_group *group, ret = fanotify_mark_add_to_mask(fsn_mark, mask, flags); out: - mutex_unlock(&group->mark_mutex); + fsnotify_group_unlock(group); fsnotify_put_mark(fsn_mark); return ret; @@ -1386,7 +1386,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */ group = fsnotify_alloc_group(&fanotify_fsnotify_ops, - FSNOTIFY_GROUP_USER); + FSNOTIFY_GROUP_USER | FSNOTIFY_GROUP_NOFS); if (IS_ERR(group)) { return PTR_ERR(group); } -- 2.35.1
