From patchwork Thu Oct 3 15:09:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13821134 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7AE51B969; Thu, 3 Oct 2024 15:09:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727968189; cv=none; b=OrunVc/l2vbMZc0Pjt4of2f9RuXVYSgmsFdHJ9lKaah/U9u4erELf1MrreiovtM0eMnKGQ+9U72Q1/Tqkpqle9MvfmqrKtCfiGcrCq7NxsDwbWTcyfwxGOuPn+rvLdniw47nw1ZaJ/6ah9+TKqBdpqHmBBIpdcBmfCt63MxVAqc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727968189; c=relaxed/simple; bh=t1erP4051fKxjeO5bhlf4vXNm9QCAZdEkniTTG/tkWU=; h=Date:Subject:From:To:Cc:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=cvkXmRsqPu68mzhO1cF2xANpK4xwS76BMTfkAqRnU+CJThBuWVtvmfOVL3JzKRnQcoSvbbALt5i6z2LCqsZtjqnElqmO/fcXAbbfixM6KSELy4m3q/BJ7p8Z4kucDzdx5Q8mFbhxJN0IDiYe9YREyQ0HNBqVLRAPHL3o7PTn4s0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b5hrQQIc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="b5hrQQIc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75C88C4CEC7; Thu, 3 Oct 2024 15:09:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727968188; bh=t1erP4051fKxjeO5bhlf4vXNm9QCAZdEkniTTG/tkWU=; h=Date:Subject:From:To:Cc:In-Reply-To:References:From; b=b5hrQQIc8tWiAxg1Dl9aDiFL6H9CqgDR/NzOUCbzp8PhFSRxed4dL4kotgU0kUvs3 KzvijsmaSQ/y1xmRxX8AxU5R39B+rDrZQYw0Ps/yYWlM+u+nAydKFxUVYW9r+o1ZVz MBlRIC0ZFppfw2K88UbOqY/bwg8fmpFRHPX4T86Bo5AKfZ2Ydjkb/UIC2c1EQ7IfBG 9I19KQpcm4/RGxErLe3uQrlPBksjCWZejM2746ByhpdyROZqPfaf62WNT8eqDmISQV Kd2tM8G21oRzwzWLi8gAZgNFGjaZtw/RpDDDYOIspFr2lTK8Pjp5kvVEJaZ9XHfSMR 2lsMz57LzArZQ== Date: Thu, 03 Oct 2024 08:09:48 -0700 Subject: [PATCH 4/4] fsdax: dax_unshare_iter needs to copy entire blocks From: "Darrick J. Wong" To: willy@infradead.org, brauner@kernel.org, djwong@kernel.org, cem@kernel.org Cc: ruansy.fnst@fujitsu.com, ruansy.fnst@fujitsu.com, linux-fsdevel@vger.kernel.org, hch@lst.de, linux-xfs@vger.kernel.org Message-ID: <172796813328.1131942.16777025316348797355.stgit@frogsfrogsfrogs> In-Reply-To: <172796813251.1131942.12184885574609980777.stgit@frogsfrogsfrogs> References: <172796813251.1131942.12184885574609980777.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Darrick J. Wong The code that copies data from srcmap to iomap in dax_unshare_iter is very very broken, which bfoster's recent fsx changes have exposed. If the pos and len passed to dax_file_unshare are not aligned to an fsblock boundary, the iter pos and length in the _iter function will reflect this unalignment. dax_iomap_direct_access always returns a pointer to the start of the kmapped fsdax page, even if its pos argument is in the middle of that page. This is catastrophic for data integrity when iter->pos is not aligned to a page, because daddr/saddr do not point to the same byte in the file as iter->pos. Hence we corrupt user data by copying it to the wrong place. If iter->pos + iomap_length() in the _iter function not aligned to a page, then we fail to copy a full block, and only partially populate the destination block. This is catastrophic for data confidentiality because we expose stale pmem contents. Fix both of these issues by aligning copy_pos/copy_len to a page boundary (remember, this is fsdax so 1 fsblock == 1 base page) so that we always copy full blocks. We're not done yet -- there's no call to invalidate_inode_pages2_range, so programs that have the file range mmap'd will continue accessing the old memory mapping after the file metadata updates have completed. Be careful with the return value -- if the unshare succeeds, we still need to return the number of bytes that the iomap iter thinks we're operating on. Cc: ruansy.fnst@fujitsu.com Fixes: d984648e428b ("fsdax,xfs: port unshare to fsdax") Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- fs/dax.c | 34 +++++++++++++++++++++++++++------- 1 file changed, 27 insertions(+), 7 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 9fbbdaa784b4..21b47402b3dc 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1262,26 +1262,46 @@ static s64 dax_unshare_iter(struct iomap_iter *iter) { struct iomap *iomap = &iter->iomap; const struct iomap *srcmap = iomap_iter_srcmap(iter); - loff_t pos = iter->pos; - loff_t length = iomap_length(iter); + loff_t copy_pos = iter->pos; + u64 copy_len = iomap_length(iter); + u32 mod; int id = 0; s64 ret = 0; void *daddr = NULL, *saddr = NULL; if (!iomap_want_unshare_iter(iter)) - return length; + return iomap_length(iter); + + /* + * Extend the file range to be aligned to fsblock/pagesize, because + * we need to copy entire blocks, not just the byte range specified. + * Invalidate the mapping because we're about to CoW. + */ + mod = offset_in_page(copy_pos); + if (mod) { + copy_len += mod; + copy_pos -= mod; + } + + mod = offset_in_page(copy_pos + copy_len); + if (mod) + copy_len += PAGE_SIZE - mod; + + invalidate_inode_pages2_range(iter->inode->i_mapping, + copy_pos >> PAGE_SHIFT, + (copy_pos + copy_len - 1) >> PAGE_SHIFT); id = dax_read_lock(); - ret = dax_iomap_direct_access(iomap, pos, length, &daddr, NULL); + ret = dax_iomap_direct_access(iomap, copy_pos, copy_len, &daddr, NULL); if (ret < 0) goto out_unlock; - ret = dax_iomap_direct_access(srcmap, pos, length, &saddr, NULL); + ret = dax_iomap_direct_access(srcmap, copy_pos, copy_len, &saddr, NULL); if (ret < 0) goto out_unlock; - if (copy_mc_to_kernel(daddr, saddr, length) == 0) - ret = length; + if (copy_mc_to_kernel(daddr, saddr, copy_len) == 0) + ret = iomap_length(iter); else ret = -EIO;