Re: [syzbot] [kernfs?] possible deadlock in kernfs_fop_llseek

[Hillf Danton]

On Wed, 03 Apr 2024 11:23:26 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15c38139180000

Test Al's idea.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  fe46a7dd189e

--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -639,6 +639,8 @@ static int kernfs_fop_open(struct inode
 	 */
 	if (has_mmap)
 		mutex_init(&of->mutex);
+	else if (file->f_mode & FMODE_WRITE)
+		mutex_init(&of->mutex);
 	else
 		mutex_init(&of->mutex);
 
--