From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: [PATCH v3] jbd2: Fix block tag checksum verification brokenness Date: Mon, 13 May 2013 14:47:50 -0700 Message-ID: <20130513214750.GB8037@blackbox.djwong.org> References: <20130510233807.GB5706@blackbox.djwong.org> <4CE338D9-F69A-4568-AA82-012FEED2E252@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , Al Viro , "linux-fsdevel@vger.kernel.org" , linux-ext4 To: "Theodore Ts'o" Return-path: Content-Disposition: inline In-Reply-To: <4CE338D9-F69A-4568-AA82-012FEED2E252@dilger.ca> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Al Viro complained of a ton of bogosity with regards to the jbd2 block tag header checksum. This one checksum is 16 bits, so cut off the upper 16 bits and treat it as a 16-bit value and don't mess around with be32* conversions. Fortunately metadata checksumming is still "experimental" and not in a shipping e2fsprogs, so there should be few users affected by this. v2: Eliminate unnecessary variables and make it clear(er) which values are 32 bits wide. v3: Add a comment about why we're only storing half of the crc32c. Reported-by: Al Viro Signed-off-by: Darrick J. Wong --- fs/jbd2/commit.c | 13 +++++++------ fs/jbd2/recovery.c | 11 +++++------ 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 0f53946..e61d722 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -343,20 +343,21 @@ static void jbd2_block_tag_csum_set(journal_t *j, journal_block_tag_t *tag, { struct page *page = bh->b_page; __u8 *addr; - __u32 csum; + __u32 csum32; if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2)) return; sequence = cpu_to_be32(sequence); addr = kmap_atomic(page); - csum = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence, - sizeof(sequence)); - csum = jbd2_chksum(j, csum, addr + offset_in_page(bh->b_data), - bh->b_size); + csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence, + sizeof(sequence)); + csum32 = jbd2_chksum(j, csum32, addr + offset_in_page(bh->b_data), + bh->b_size); kunmap_atomic(addr); - tag->t_checksum = cpu_to_be32(csum); + /* We only have space to store the lower 16 bits of the crc32c. */ + tag->t_checksum = cpu_to_be16(csum32); } /* * jbd2_journal_commit_transaction diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c index 626846b..d4851464 100644 --- a/fs/jbd2/recovery.c +++ b/fs/jbd2/recovery.c @@ -399,18 +399,17 @@ static int jbd2_commit_block_csum_verify(journal_t *j, void *buf) static int jbd2_block_tag_csum_verify(journal_t *j, journal_block_tag_t *tag, void *buf, __u32 sequence) { - __u32 provided, calculated; + __u32 csum32; if (!JBD2_HAS_INCOMPAT_FEATURE(j, JBD2_FEATURE_INCOMPAT_CSUM_V2)) return 1; sequence = cpu_to_be32(sequence); - calculated = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence, - sizeof(sequence)); - calculated = jbd2_chksum(j, calculated, buf, j->j_blocksize); - provided = be32_to_cpu(tag->t_checksum); + csum32 = jbd2_chksum(j, j->j_csum_seed, (__u8 *)&sequence, + sizeof(sequence)); + csum32 = jbd2_chksum(j, csum32, buf, j->j_blocksize); - return provided == cpu_to_be32(calculated); + return tag->t_checksum == cpu_to_be16(csum32); } static int do_one_pass(journal_t *journal,