From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36806 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751023AbdEWKdq (ORCPT ); Tue, 23 May 2017 06:33:46 -0400 Subject: Patch "dax: fix data corruption when fault races with write" has been added to the 4.11-stable tree To: jack@suse.cz, akpm@linux-foundation.org, dan.j.williams@intel.com, gregkh@linuxfoundation.org, ross.zwisler@linux.intel.com, torvalds@linux-foundation.org Cc: , From: Date: Tue, 23 May 2017 12:33:27 +0200 Message-ID: <149553560719580@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled dax: fix data corruption when fault races with write to the 4.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: dax-fix-data-corruption-when-fault-races-with-write.patch and it can be found in the queue-4.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 13e451fdc1af05568ea379d71c02a126295d2244 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 12 May 2017 15:46:57 -0700 Subject: dax: fix data corruption when fault races with write From: Jan Kara commit 13e451fdc1af05568ea379d71c02a126295d2244 upstream. Currently DAX read fault can race with write(2) in the following way: CPU1 - write(2) CPU2 - read fault dax_iomap_pte_fault() ->iomap_begin() - sees hole dax_iomap_rw() iomap_apply() ->iomap_begin - allocates blocks dax_iomap_actor() invalidate_inode_pages2_range() - there's nothing to invalidate grab_mapping_entry() - we add zero page in the radix tree and map it to page tables The result is that hole page is mapped into page tables (and thus zeros are seen in mmap) while file has data written in that place. Fix the problem by locking exception entry before mapping blocks for the fault. That way we are sure invalidate_inode_pages2_range() call for racing write will either block on entry lock waiting for the fault to finish (and unmap stale page tables after that) or read fault will see already allocated blocks by write(2). Fixes: 9f141d6ef6258a3a37a045842d9ba7e68f368956 Link: http://lkml.kernel.org/r/20170510085419.27601-5-jack@suse.cz Signed-off-by: Jan Kara Signed-off-by: Ross Zwisler Reviewed-by: Ross Zwisler Cc: Dan Williams Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/dax.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) --- a/fs/dax.c +++ b/fs/dax.c @@ -1124,23 +1124,23 @@ static int dax_iomap_pte_fault(struct vm if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page) flags |= IOMAP_WRITE; + entry = grab_mapping_entry(mapping, vmf->pgoff, 0); + if (IS_ERR(entry)) + return dax_fault_return(PTR_ERR(entry)); + /* * Note that we don't bother to use iomap_apply here: DAX required * the file system block size to be equal the page size, which means * that we never have to deal with more than a single extent here. */ error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap); - if (error) - return dax_fault_return(error); - if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { - vmf_ret = dax_fault_return(-EIO); /* fs corruption? */ - goto finish_iomap; + if (error) { + vmf_ret = dax_fault_return(error); + goto unlock_entry; } - - entry = grab_mapping_entry(mapping, vmf->pgoff, 0); - if (IS_ERR(entry)) { - vmf_ret = dax_fault_return(PTR_ERR(entry)); - goto finish_iomap; + if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { + error = -EIO; /* fs corruption? */ + goto error_finish_iomap; } sector = dax_iomap_sector(&iomap, pos); @@ -1162,13 +1162,13 @@ static int dax_iomap_pte_fault(struct vm } if (error) - goto error_unlock_entry; + goto error_finish_iomap; __SetPageUptodate(vmf->cow_page); vmf_ret = finish_fault(vmf); if (!vmf_ret) vmf_ret = VM_FAULT_DONE_COW; - goto unlock_entry; + goto finish_iomap; } switch (iomap.type) { @@ -1188,7 +1188,7 @@ static int dax_iomap_pte_fault(struct vm case IOMAP_HOLE: if (!(vmf->flags & FAULT_FLAG_WRITE)) { vmf_ret = dax_load_hole(mapping, &entry, vmf); - goto unlock_entry; + goto finish_iomap; } /*FALLTHRU*/ default: @@ -1197,10 +1197,8 @@ static int dax_iomap_pte_fault(struct vm break; } - error_unlock_entry: + error_finish_iomap: vmf_ret = dax_fault_return(error) | major; - unlock_entry: - put_locked_mapping_entry(mapping, vmf->pgoff, entry); finish_iomap: if (ops->iomap_end) { int copied = PAGE_SIZE; @@ -1215,6 +1213,8 @@ static int dax_iomap_pte_fault(struct vm */ ops->iomap_end(inode, pos, PAGE_SIZE, copied, flags, &iomap); } + unlock_entry: + put_locked_mapping_entry(mapping, vmf->pgoff, entry); return vmf_ret; } Patches currently in stable-queue which might be from jack@suse.cz are queue-4.11/dax-fix-data-corruption-when-fault-races-with-write.patch queue-4.11/fanotify-don-t-expose-eopenstale-to-userspace.patch