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Patch "ext4: avoid modifying checksum fields directly during checksum verification" has been added to the 4.7-stable tree

PATCH [email protected] 1 participant 1 message Sep 9, 2016

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This is a note to let you know that I've just added the patch titled

ext4: avoid modifying checksum fields directly during checksum verification

to the 4.7-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:
ext4-avoid-modifying-checksum-fields-directly-during-checksum-verification.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From b47820edd1634dc1208f9212b7ecfb4230610a23 Mon Sep 17 00:00:00 2001

From: Daeho Jeong <[email protected]>
Date: Sun, 3 Jul 2016 17:51:39 -0400
Subject: ext4: avoid modifying checksum fields directly during checksum verification

From: Daeho Jeong <[email protected]>

commit b47820edd1634dc1208f9212b7ecfb4230610a23 upstream.

We temporally change checksum fields in buffers of some types of metadata into '0' for verifying the checksum values. By doing this without locking the buffer, some metadata's checksums, which are being committed or written back to the storage, could be damaged. In our test, several metadata blocks were found with damaged metadata checksum value during recovery process. When we only verify the checksum value, we have to avoid modifying checksum fields directly.

Signed-off-by Daeho Jeong <[email protected]>
Signed-off-by Youngjin Gil <[email protected]>
Signed-off-by Theodore Ts'o <[email protected]>
Reviewed-by Darrick J. Wong <[email protected]>
Cc Török Edwin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 fs/ext4/inode.c |   38 ++++++++++++++++++++++----------------
 fs/ext4/namei.c |    9 ++++-----
 fs/ext4/super.c |   18 +++++++++---------
 fs/ext4/xattr.c |   13 +++++++------
 4 files changed, 42 insertions(+), 36 deletions(-)
fs/ext4/inode.c +22 -16
@@ -51,25 +51,31 @@ static __u32 ext4_inode_csum(struct inod
 			      struct ext4_inode_info *ei)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	__u16 csum_lo;
-	__u16 csum_hi = 0;
 	__u32 csum;
+	__u16 dummy_csum = 0;
+	int offset = offsetof(struct ext4_inode, i_checksum_lo);
+	unsigned int csum_size = sizeof(dummy_csum);
 
-	csum_lo = le16_to_cpu(raw->i_checksum_lo);
-	raw->i_checksum_lo = 0;
-	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
-	    EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi)) {
-		csum_hi = le16_to_cpu(raw->i_checksum_hi);
-		raw->i_checksum_hi = 0;
-	}
-
-	csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)raw,
-			   EXT4_INODE_SIZE(inode->i_sb));
+	csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)raw, offset);
+	csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, csum_size);
+	offset += csum_size;
+	csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
+			   EXT4_GOOD_OLD_INODE_SIZE - offset);
 
-	raw->i_checksum_lo = cpu_to_le16(csum_lo);
-	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE &&
-	    EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi))
-		raw->i_checksum_hi = cpu_to_le16(csum_hi);
+	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
+		offset = offsetof(struct ext4_inode, i_checksum_hi);
+		csum = ext4_chksum(sbi, csum, (__u8 *)raw +
+				   EXT4_GOOD_OLD_INODE_SIZE,
+				   offset - EXT4_GOOD_OLD_INODE_SIZE);
+		if (EXT4_FITS_IN_INODE(raw, ei, i_checksum_hi)) {
+			csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum,
+					   csum_size);
+			offset += csum_size;
+			csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
+					   EXT4_INODE_SIZE(inode->i_sb) -
+					   offset);
+		}
+	}
 
 	return csum;
 }
fs/ext4/namei.c +4 -5
@@ -420,15 +420,14 @@ static __le32 ext4_dx_csum(struct inode
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	__u32 csum;
-	__le32 save_csum;
 	int size;
+	__u32 dummy_csum = 0;
+	int offset = offsetof(struct dx_tail, dt_checksum);
 
 	size = count_offset + (count * sizeof(struct dx_entry));
-	save_csum = t->dt_checksum;
-	t->dt_checksum = 0;
 	csum = ext4_chksum(sbi, ei->i_csum_seed, (__u8 *)dirent, size);
-	csum = ext4_chksum(sbi, csum, (__u8 *)t, sizeof(struct dx_tail));
-	t->dt_checksum = save_csum;
+	csum = ext4_chksum(sbi, csum, (__u8 *)t, offset);
+	csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, sizeof(dummy_csum));
 
 	return cpu_to_le32(csum);
 }
fs/ext4/super.c +9 -9
@@ -2068,23 +2068,25 @@ failed:
 static __le16 ext4_group_desc_csum(struct super_block *sb, __u32 block_group,
 				   struct ext4_group_desc *gdp)
 {
-	int offset;
+	int offset = offsetof(struct ext4_group_desc, bg_checksum);
 	__u16 crc = 0;
 	__le32 le_group = cpu_to_le32(block_group);
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
 	if (ext4_has_metadata_csum(sbi->s_sb)) {
 		/* Use new metadata_csum algorithm */
-		__le16 save_csum;
 		__u32 csum32;
+		__u16 dummy_csum = 0;
 
-		save_csum = gdp->bg_checksum;
-		gdp->bg_checksum = 0;
 		csum32 = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&le_group,
 				     sizeof(le_group));
-		csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp,
-				     sbi->s_desc_size);
-		gdp->bg_checksum = save_csum;
+		csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp, offset);
+		csum32 = ext4_chksum(sbi, csum32, (__u8 *)&dummy_csum,
+				     sizeof(dummy_csum));
+		offset += sizeof(dummy_csum);
+		if (offset < sbi->s_desc_size)
+			csum32 = ext4_chksum(sbi, csum32, (__u8 *)gdp + offset,
+					     sbi->s_desc_size - offset);
 
 		crc = csum32 & 0xFFFF;
 		goto out;

@@ -2094,8 +2096,6 @@ static __le16 ext4_group_desc_csum(struc
 	if (!ext4_has_feature_gdt_csum(sb))
 		return 0;
 
-	offset = offsetof(struct ext4_group_desc, bg_checksum);
-
 	crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
 	crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
 	crc = crc16(crc, (__u8 *)gdp, offset);
fs/ext4/xattr.c +7 -6
@@ -121,17 +121,18 @@ static __le32 ext4_xattr_block_csum(stru
 {
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	__u32 csum;
-	__le32 save_csum;
 	__le64 dsk_block_nr = cpu_to_le64(block_nr);
+	__u32 dummy_csum = 0;
+	int offset = offsetof(struct ext4_xattr_header, h_checksum);
 
-	save_csum = hdr->h_checksum;
-	hdr->h_checksum = 0;
 	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&dsk_block_nr,
 			   sizeof(dsk_block_nr));
-	csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
-			   EXT4_BLOCK_SIZE(inode->i_sb));
+	csum = ext4_chksum(sbi, csum, (__u8 *)hdr, offset);
+	csum = ext4_chksum(sbi, csum, (__u8 *)&dummy_csum, sizeof(dummy_csum));
+	offset += sizeof(dummy_csum);
+	csum = ext4_chksum(sbi, csum, (__u8 *)hdr + offset,
+			   EXT4_BLOCK_SIZE(inode->i_sb) - offset);
 
-	hdr->h_checksum = save_csum;
 	return cpu_to_le32(csum);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/ext4-avoid-modifying-checksum-fields-directly-during-checksum-verification.patch