From: Jiachen Zhang zhangjiachen.jaycee@bytedance.com
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@bytedance.com Signed-off-by: Jiachen Zhang zhangjiachen.jaycee@bytedance.com Signed-off-by: Tianci Zhang zhangtianci.1997@bytedance.com Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles") Cc: stable@vger.kernel.org # v4.16 Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/overlayfs/export.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -257,7 +257,7 @@ 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;
bytes = ovl_dentry_to_fid(dentry, fid, buflen);