From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: [RFC PATCH V3 1/2] null_blk: Null pointer deference problem in alloc_page_buffers Date: Tue, 21 Jan 2014 16:59:59 +0530 Message-ID: <1390303800-22422-2-git-send-email-raghavendra.kt@linux.vnet.ibm.com> References: <1390303800-22422-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Raghavendra K T , Sumanth To: Alexander Viro , Matias Bjorling , Jens Axboe , Andrew Morton , Yuanhan Liu , "Darrick J. Wong" , Jan Kara , Johannes Weiner , Zhang Yanfei , Jeff Return-path: In-Reply-To: <1390303800-22422-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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: [] 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 Signed-off-by: Raghavendra K T --- 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) { -- 1.7.11.7