From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suresh Jayaraman Subject: [PATCH 31/31] swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL Date: Thu, 1 Oct 2009 19:41:09 +0530 Message-ID: <1254406269-16771-1-git-send-email-sjayaraman@suse.de> Cc: netdev@vger.kernel.org, Neil Brown , Miklos Szeredi , Wouter Verhelst , Peter Zijlstra , trond.myklebust@fys.uio.no, Suresh Jayaraman To: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Return-path: Sender: owner-linux-mm@kvack.org List-Id: netdev.vger.kernel.org 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 is not 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 --- mm/swapfile.c | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) Index: mmotm/mm/swapfile.c =================================================================== --- mmotm.orig/mm/swapfile.c +++ mmotm/mm/swapfile.c @@ -160,10 +160,12 @@ static int discard_swap(struct swap_info continue; } - err = blkdev_issue_discard(si->bdev, start_block, + if (si->bdev) { + err = blkdev_issue_discard(si->bdev, start_block, nr_blocks, GFP_KERNEL); - if (err) - break; + if (err) + break; + } cond_resched(); } @@ -199,9 +201,11 @@ static void discard_swap_cluster(struct start_block <<= PAGE_SHIFT - 9; nr_blocks <<= PAGE_SHIFT - 9; - if (blkdev_issue_discard(si->bdev, start_block, + if (si->bdev) { + if (blkdev_issue_discard(si->bdev, start_block, nr_blocks, GFP_NOIO)) - break; + break; + } } lh = se->list.next; @@ -1991,12 +1995,14 @@ SYSCALL_DEFINE2(swapon, const char __use 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); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org