Commit 3bd0f0c7 authored Sep 30, 2009 by Suresh Jayaraman Committed by Jens Axboe Oct 01, 2009

swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL



While testing Swap over NFS patchset, I noticed an oops that was triggered
during swapon. Investigating further, the NULL pointer deference is due to the
SSD device check/optimization in the swapon code that assumes s_bdev could never
be NULL.

inode->i_sb->s_bdev could be NULL in a few cases. For e.g. one such case is
loopback NFS mount, there could be others as well. Fix this by ensuring s_bdev
is not NULL before we try to deference s_bdev.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

parent a112a71d

mm/swapfile.c

+7 −5

Original line number	Original line	Diff line number	Diff line
	@@ -1974,12 +1974,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
	goto bad_swap;		goto bad_swap;
	}		}

			if (p->bdev) {
	if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
	p->flags \|= SWP_SOLIDSTATE;		p->flags \|= SWP_SOLIDSTATE;
	p->cluster_next = 1 + (random32() % p->highest_bit);		p->cluster_next = 1 + (random32() % p->highest_bit);
	}		}
	if (discard_swap(p) == 0)		if (discard_swap(p) == 0)
	p->flags \|= SWP_DISCARDABLE;		p->flags \|= SWP_DISCARDABLE;
			}

	mutex_lock(&swapon_mutex);		mutex_lock(&swapon_mutex);
	spin_lock(&swap_lock);		spin_lock(&swap_lock);