6.8-stable review patch. If anyone has any objections, please let me know.
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From: Amir Goldstein amir73il@gmail.com
commit 16b52bbee4823b01ab7fe3919373c981a38f3797 upstream.
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 viro@zeniv.linux.org.uk Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/kernfs/file.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -634,11 +634,18 @@ static int kernfs_fop_open(struct inode * 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);