[BUG] fs/afs/flock: possible sleep-in-atomic bugs in afs_do_setlk

From: Jia-Ju Bai
Date: Sat Oct 07 2017 - 06:11:43 EST

According to fs/afs/flock.c, the kernel may sleep under a spinlock,
and the function call paths are:
afs_do_setlk (acquire the spinlock: inode->i_lock)
schedule --> may sleep

afs_do_setlk (acquire the spinlock: inode->i_lock)
wait_event_interruptible --> may sleep

These bugs may be introduced by only considering "vnode->lock" but ignoring "inode->i_lock".

A possible fix is to unlock "inode->i_lock" before calling afs_vnode_fetch_status and wait_event_interruptible, and lock "inode->i_lock" again after them.

These bugs are found by my static analysis tool and my code review.

Jia-Ju Bai