From dd524b7f317de8d31d638cbfdc7be4cf9b770e42 Mon Sep 17 00:00:00 2001 From: Jiachen Zhang Date: Thu, 28 Jul 2022 19:49:15 +0800 Subject: ovl: drop WARN_ON() dentry is NULL in ovl_encode_fh() 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 Signed-off-by: Jiachen Zhang Signed-off-by: Tianci Zhang Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles") Cc: # v4.16 Signed-off-by: Miklos Szeredi --- fs/overlayfs/export.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/overlayfs/export.c') diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 2eada97bbd23..e065a5b9a442 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -259,7 +259,7 @@ static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len, return FILEID_INVALID; dentry = d_find_any_alias(inode); - if (WARN_ON(!dentry)) + if (!dentry) return FILEID_INVALID; bytes = ovl_dentry_to_fid(ofs, dentry, fid, buflen); -- cgit v1.2.3