From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id D14C27F51 for ; Thu, 7 Jan 2016 23:28:18 -0600 (CST) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay2.corp.sgi.com (Postfix) with ESMTP id B62BA304039 for ; Thu, 7 Jan 2016 21:28:15 -0800 (PST) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by cuda.sgi.com with ESMTP id ApuzZACdMC0luqc8 for ; Thu, 07 Jan 2016 21:28:13 -0800 (PST) From: Ross Zwisler Subject: [PATCH v8 1/9] dax: fix NULL pointer dereference in __dax_dbg() Date: Thu, 7 Jan 2016 22:27:51 -0700 Message-Id: <1452230879-18117-2-git-send-email-ross.zwisler@linux.intel.com> In-Reply-To: <1452230879-18117-1-git-send-email-ross.zwisler@linux.intel.com> References: <1452230879-18117-1-git-send-email-ross.zwisler@linux.intel.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: linux-kernel@vger.kernel.org Cc: Dave Hansen , "J. Bruce Fields" , linux-mm@kvack.org, Andreas Dilger , "H. Peter Anvin" , Jeff Layton , Dan Williams , linux-nvdimm@lists.01.org, x86@kernel.org, Ingo Molnar , Matthew Wilcox , Ross Zwisler , linux-ext4@vger.kernel.org, xfs@oss.sgi.com, Alexander Viro , Thomas Gleixner , Theodore Ts'o , Jan Kara , linux-fsdevel@vger.kernel.org, Andrew Morton , Matthew Wilcox In __dax_pmd_fault() we currently assume that get_block() will always set bh.b_bdev and we unconditionally dereference it in __dax_dbg(). This assumption isn't always true - when called for reads of holes ext4_dax_mmap_get_block() returns a buffer head where bh->b_bdev is never set. I hit this BUG while testing the DAX PMD fault path. Instead, initialize bh.b_bdev before passing bh into get_block(). It is possible that the filesystem's get_block() will update bh.b_bdev, and this is fine - we just want to initialize bh.b_bdev to something reasonable so that the calls to __dax_dbg() work and print something useful. Signed-off-by: Ross Zwisler Cc: Dan Williams --- fs/dax.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/dax.c b/fs/dax.c index 7af8797..513bba5 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -624,6 +624,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, } memset(&bh, 0, sizeof(bh)); + bh.b_bdev = inode->i_sb->s_bdev; block = (sector_t)pgoff << (PAGE_SHIFT - blkbits); bh.b_size = PMD_SIZE; -- 2.5.0 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs