Commit 9967d8ac authored Jan 21, 2014 by Raghavendra K T Committed by Jens Axboe Jan 21, 2014

null_blk: Null pointer deference problem in alloc_page_buffers



 If we load the null_blk module with bs=8k we get following oops:
[ 3819.812190] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[ 3819.812387] IP: [<ffffffff81170aa5>] create_empty_buffers+0x28/0xaf
[ 3819.812527] PGD 219244067 PUD 215a06067 PMD 0
[ 3819.812640] Oops: 0000 [#1] SMP
[ 3819.812772] Modules linked in: null_blk(+)

 Fix that by resetting block size to PAGE_SIZE if it is greater than PAGE_SIZE

Reported-by: Sumanth <sumantk2@linux.vnet.ibm.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Reviewed-by: Matias Bjorling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 26d58057

drivers/block/null_blk.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -622,6 +622,11 @@ static int __init null_init(void)
		irqmode = NULL_IRQ_NONE;
		}
		#endif
		if (bs > PAGE_SIZE) {
		pr_warn("null_blk: invalid block size\n");
		pr_warn("null_blk: defaults block size to %lu\n", PAGE_SIZE);
		bs = PAGE_SIZE;
		}

		if (queue_mode == NULL_Q_MQ && use_per_node_hctx) {
		if (submit_queues < nr_online_nodes) {

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