From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (Postfix) with ESMTP id BDF3B7F37 for ; Tue, 12 Jan 2016 03:34:58 -0600 (CST) Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by relay1.corp.sgi.com (Postfix) with ESMTP id AC71C8F8035 for ; Tue, 12 Jan 2016 01:34:58 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id 9EYBX6Wnvn5WXGhd (version=TLSv1 cipher=ECDHE-RSA-AES256-SHA bits=256 verify=NO) for ; Tue, 12 Jan 2016 01:34:56 -0800 (PST) Date: Tue, 12 Jan 2016 10:34:58 +0100 From: Jan Kara Subject: Re: [PATCH v8 1/9] dax: fix NULL pointer dereference in __dax_dbg() Message-ID: <20160112093458.GR6262@quack.suse.cz> References: <1452230879-18117-1-git-send-email-ross.zwisler@linux.intel.com> <1452230879-18117-2-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1452230879-18117-2-git-send-email-ross.zwisler@linux.intel.com> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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: Ross Zwisler 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 , linux-ext4@vger.kernel.org, xfs@oss.sgi.com, Alexander Viro , Thomas Gleixner , Theodore Ts'o , linux-kernel@vger.kernel.org, Jan Kara , linux-fsdevel@vger.kernel.org, Andrew Morton , Matthew Wilcox On Thu 07-01-16 22:27:51, Ross Zwisler wrote: > 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 Looks good. But don't you need to do the same for __dax_fault(), dax_zero_page_range() and similar places passing bh to dax functions? Honza > --- > 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 > > -- Jan Kara SUSE Labs, CR _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs