From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758429AbbIVRqw (ORCPT ); Tue, 22 Sep 2015 13:46:52 -0400 Received: from mga11.intel.com ([192.55.52.93]:23557 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758162AbbIVRqs (ORCPT ); Tue, 22 Sep 2015 13:46:48 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,574,1437462000"; d="scan'208";a="566395545" From: Ross Zwisler To: linux-kernel@vger.kernel.org Cc: Ross Zwisler , Alexander Viro , Matthew Wilcox , "Kirill A. Shutemov" , linux-nvdimm@ml01.01.org, Dan Williams , Dave Chinner , linux-fsdevel@vger.kernel.org Subject: [PATCH] dax: fix NULL pointer in __dax_pmd_fault() Date: Tue, 22 Sep 2015 11:46:19 -0600 Message-Id: <1442943979-1931-1-git-send-email-ross.zwisler@linux.intel.com> X-Mailer: git-send-email 2.1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit: commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX") moved some code in __dax_pmd_fault() that was responsible for zeroing newly allocated PMD pages. The new location didn't properly set up 'kaddr', though, so when run this code resulted in a NULL pointer BUG. Fix this by getting the correct 'kaddr' via bdev_direct_access(), and only make the second call to bdev_direct_access() if we don't already have a PFN from the first call. Signed-off-by: Ross Zwisler Reported-by: Dan Williams --- fs/dax.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 7ae6df7..08ac2bd 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -532,7 +532,7 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, void __pmem *kaddr; pgoff_t size, pgoff; sector_t block, sector; - unsigned long pfn; + unsigned long pfn = 0; int result = 0; /* Fall back to PTEs if we're going to COW */ @@ -569,8 +569,20 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) goto fallback; + sector = bh.b_blocknr << (blkbits - 9); + if (buffer_unwritten(&bh) || buffer_new(&bh)) { int i; + + length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, + bh.b_size); + if (length < 0) { + result = VM_FAULT_SIGBUS; + goto out; + } + if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) + goto fallback; + for (i = 0; i < PTRS_PER_PMD; i++) clear_pmem(kaddr + i * PAGE_SIZE, PAGE_SIZE); wmb_pmem(); @@ -623,15 +635,16 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, result = VM_FAULT_NOPAGE; spin_unlock(ptl); } else { - sector = bh.b_blocknr << (blkbits - 9); - length = bdev_direct_access(bh.b_bdev, sector, &kaddr, &pfn, - bh.b_size); - if (length < 0) { - result = VM_FAULT_SIGBUS; - goto out; + if (pfn == 0) { + length = bdev_direct_access(bh.b_bdev, sector, &kaddr, + &pfn, bh.b_size); + if (length < 0) { + result = VM_FAULT_SIGBUS; + goto out; + } + if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) + goto fallback; } - if ((length < PMD_SIZE) || (pfn & PG_PMD_COLOUR)) - goto fallback; result |= vmf_insert_pfn_pmd(vma, address, pmd, pfn, write); } -- 2.1.0