This is a note to let you know that I've just added the patch titled ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh() to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ovl-drop-warn_on-dentry-is-null-in-ovl_encode_fh.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From dd524b7f317de8d31d638cbfdc7be4cf9b770e42 Mon Sep 17 00:00:00 2001 From: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx> Date: Thu, 28 Jul 2022 19:49:15 +0800 Subject: ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh() From: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx> commit dd524b7f317de8d31d638cbfdc7be4cf9b770e42 upstream. Some code paths cannot guarantee the inode have any dentry alias. So WARN_ON() all !dentry may flood the kernel logs. For example, when an overlayfs inode is watched by inotifywait (1), and someone is trying to read the /proc/$(pidof inotifywait)/fdinfo/INOTIFY_FD, at that time if the dentry has been reclaimed by kernel (such as echo 2 > /proc/sys/vm/drop_caches), there will be a WARN_ON(). The printed call stack would be like: ? show_mark_fhandle+0xf0/0xf0 show_mark_fhandle+0x4a/0xf0 ? show_mark_fhandle+0xf0/0xf0 ? seq_vprintf+0x30/0x50 ? seq_printf+0x53/0x70 ? show_mark_fhandle+0xf0/0xf0 inotify_fdinfo+0x70/0x90 show_fdinfo.isra.4+0x53/0x70 seq_show+0x130/0x170 seq_read+0x153/0x440 vfs_read+0x94/0x150 ksys_read+0x5f/0xe0 do_syscall_64+0x59/0x1e0 entry_SYSCALL_64_after_hwframe+0x44/0xa9 So let's drop WARN_ON() to avoid kernel log flooding. Reported-by: Hongbo Yin <yinhongbo@xxxxxxxxxxxxx> Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@xxxxxxxxxxxxx> Signed-off-by: Tianci Zhang <zhangtianci.1997@xxxxxxxxxxxxx> Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles") Cc: <stable@xxxxxxxxxxxxxxx> # v4.16 Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/overlayfs/export.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -277,7 +277,7 @@ static int ovl_encode_fh(struct inode *i return FILEID_INVALID; dentry = d_find_any_alias(inode); - if (WARN_ON(!dentry)) + if (!dentry) return FILEID_INVALID; type = ovl_dentry_to_fh(dentry, fid, max_len); Patches currently in stable-queue which might be from zhangjiachen.jaycee@xxxxxxxxxxxxx are queue-4.19/ovl-drop-warn_on-dentry-is-null-in-ovl_encode_fh.patch