From 16b52bbee4823b01ab7fe3919373c981a38f3797 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 5 Apr 2024 17:56:35 +0300 Subject: [PATCH] kernfs: annotate different lockdep class for of->mutex of writable files The writable file /sys/power/resume may call vfs lookup helpers for arbitrary paths and readonly files can be read by overlayfs from vfs helpers when sysfs is a lower layer of overalyfs. To avoid a lockdep warning of circular dependency between overlayfs inode lock and kernfs of->mutex, use a different lockdep class for writable and readonly kernfs files. Reported-by: syzbot+9a5b0ced8b1bfb238b56@syzkaller.appspotmail.com Fixes: 0fedefd4c4e3 ("kernfs: sysfs: support custom llseek method for sysfs entries") Suggested-by: Al Viro Signed-off-by: Amir Goldstein Signed-off-by: Al Viro --- fs/kernfs/file.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index e9df2f87072c..8502ef68459b 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -636,11 +636,18 @@ static int kernfs_fop_open(struct inode *inode, struct file *file) * each file a separate locking class. Let's differentiate on * whether the file has mmap or not for now. * - * Both paths of the branch look the same. They're supposed to + * For similar reasons, writable and readonly files are given different + * lockdep key, because the writable file /sys/power/resume may call vfs + * lookup helpers for arbitrary paths and readonly files can be read by + * overlayfs from vfs helpers when sysfs is a lower layer of overalyfs. + * + * All three cases look the same. They're supposed to * look that way and give @of->mutex different static lockdep keys. */ if (has_mmap) mutex_init(&of->mutex); + else if (file->f_mode & FMODE_WRITE) + mutex_init(&of->mutex); else mutex_init(&of->mutex); -- 2.20.1