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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>
This commit is contained in:
Suresh Jayaraman 2009-09-30 10:53:48 +02:00 committed by Jens Axboe
parent a112a71d45
commit 3bd0f0c763
1 changed files with 7 additions and 5 deletions
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12
mm/swapfile.c
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@ -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);