linux-kernel - [BUG] fs: jffs2: possible sleep-in-atomic-context bugs in jffs2

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Date:   Mon, 13 Aug 2018 11:32:39 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     dhowells@...hat.com
Cc:     linux-afs@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [BUG] fs: jffs2: possible sleep-in-atomic-context bugs in jffs2_iget

The kernel may sleep with holding a spinlock.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] schedule
fs/inode.c, 1916: schedule in __wait_on_freeing_inode
fs/inode.c, 826: __wait_on_freeing_inode in find_inode_fast
fs/inode.c, 1107: find_inode_fast in iget_locked
fs/jffs2/fs.c, 263: iget_locked in jffs2_iget
fs/jffs2/fs.c, 665: jffs2_iget in jffs2_gc_fetch_inode
fs/jffs2/wbuf.c, 505: jffs2_gc_fetch_inode in jffs2_wbuf_recover
fs/jffs2/wbuf.c, 462: spin_lock in jffs2_wbuf_recover

[FUNC] mutex_lock_nested
fs/jffs2/fs.c, 273: mutex_lock_nested in jffs2_iget
fs/jffs2/fs.c, 665: jffs2_iget in jffs2_gc_fetch_inode
fs/jffs2/wbuf.c, 505: jffs2_gc_fetch_inode in jffs2_wbuf_recover
fs/jffs2/wbuf.c, 462: spin_lock in jffs2_wbuf_recover

I do not find a good way to fix, so I only report.
Maybe the spinlock should be released before calling jffs2_iget(), and 
then be acquired again.
This is found by my static analysis tool (DSAC).


Thanks,
Jia-Ju Bai