From 3bd0f0c763e497c8674b28e3df2732f48683dabd Mon Sep 17 00:00:00 2001 From: Suresh Jayaraman Date: Wed, 30 Sep 2009 10:53:48 +0200 Subject: [PATCH] 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 Signed-off-by: Jens Axboe --- mm/swapfile.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 4de7f02f820b..a1bc6b9af9a2 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1974,12 +1974,14 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) goto bad_swap; } - if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { - p->flags |= SWP_SOLIDSTATE; - p->cluster_next = 1 + (random32() % p->highest_bit); + if (p->bdev) { + if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { + p->flags |= SWP_SOLIDSTATE; + p->cluster_next = 1 + (random32() % p->highest_bit); + } + if (discard_swap(p) == 0) + p->flags |= SWP_DISCARDABLE; } - if (discard_swap(p) == 0) - p->flags |= SWP_DISCARDABLE; mutex_lock(&swapon_mutex); spin_lock(&swap_lock); -- 2.30.2