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SubjectRe: [RFC PATCH V3 1/2] null_blk: Null pointer deference problem in alloc_page_buffers
On 01/21/2014 03:29 AM, Raghavendra K T wrote:
> 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>
> ---
> drivers/block/null_blk.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
> index a2e69d2..a01d7f6 100644
> --- a/drivers/block/null_blk.c
> +++ b/drivers/block/null_blk.c
> @@ -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) {
>

Reviewed-by: Matias Bjorling <m@bjorling.me>


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