Messages in this thread Patch in this message | | | Date | Tue, 29 Sep 2009 17:53:29 +0530 | From | Suresh Jayaraman <> | Subject | [PATCH] swapfile: avoid NULL pointer dereference in swapon when s_bdev is NULL |
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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 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> --- mm/swapfile.c | 12 +++++++----- 1 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c index 4de7f02..a1bc6b9 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);
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