If a frozen bdev does not have a filesystem sitting on top of it any subsequent nested freeze will cause a null pointer dereference because freeze_bdev() calls drop_super() unconditionally. drop_super() should be called only when there is a superblock to drop. Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: Josef Bacik <jbacik@xxxxxxxxxxxx> Cc: Eric Sandeen <sandeen@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Dave Chinner <dchinner@xxxxxxxxxx> Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx> Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx> --- diff -urNp linux-3.8-rc1-orig/fs/block_dev.c linux-3.8-rc1/fs/block_dev.c --- linux-3.8-rc1-orig/fs/block_dev.c 2012-12-25 11:38:05.072018000 +0900 +++ linux-3.8-rc1/fs/block_dev.c 2012-12-25 11:50:43.060018000 +0900 @@ -227,8 +227,8 @@ struct super_block *freeze_bdev(struct b * to freeze_bdev grab an active reference and only the last * thaw_bdev drops it. */ - sb = get_super(bdev); - drop_super(sb); + if ((sb = get_super(bdev)) != NULL) + drop_super(sb); mutex_unlock(&bdev->bd_fsfreeze_mutex); return sb; } -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
