On Wed, Apr 12, 2023 at 10:11:08PM +0900, Tetsuo Handa wrote: > syzbot is reporting circular locking dependency between ntfs_file_mmap() > (which has mm->mmap_lock => ni->ni_lock dependency) and ntfs_fiemap() > (which has ni->ni_lock => mm->mmap_lock dependency). > > Since ni_fiemap() is called by ioctl(FS_IOC_FIEMAP) via optional > "struct inode_operations"->fiemap callback, I assume that importance of > ni_fiemap() is lower than ntfs_file_mmap(). > > Also, since Documentation/filesystems/fiemap.rst says that "If an error > is encountered while copying the extent to user memory, -EFAULT will be > returned.", I assume that ioctl(FS_IOC_FIEMAP) users can handle -EFAULT > error. What? No, that doesn't mean "You can return -EFAULT because random luck". That means "If you pass it an invalid address, you'll get -EFAULT back". NACK.
