Messages in this thread Patch in this message | | | 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 |
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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 <sjayaraman@suse.de> --- 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);
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