linux-kernel - [ 099/122] ext4: use s_csum_seed instead of i_csum

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20120807221958.408099265@linuxfoundation.org>
Date:	Tue,  7 Aug 2012 15:26:27 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Tao Ma <boyu.mt@...bao.com>,
	"Theodore Tso" <tytso@....edu>,
	"Darrick J. Wong" <djwong@...ibm.com>
Subject: [ 099/122] ext4: use s_csum_seed instead of i_csum_seed for xattr block

From: Greg KH <gregkh@...uxfoundation.org>

3.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tao Ma <boyu.mt@...bao.com>

commit 41eb70dde42b2360074a559a6f1fc49860a50179 upstream.

In xattr block operation, we use h_refcount to indicate whether the
xattr block is shared among many inodes. And xattr block csum uses
s_csum_seed if it is shared and i_csum_seed if it belongs to
one inode. But this has a problem. So consider the block is shared
first bewteen inode A and B, and B has some xattr update and CoW
the xattr block. When it updates the *old* xattr block(because
of the h_refcount change) and calls ext4_xattr_release_block, we
has no idea that inode A is the real owner of the *old* xattr
block and we can't use the i_csum_seed of inode A either in xattr
block csum calculation. And I don't think we have an easy way to
find inode A.

So this patch just removes the tricky i_csum_seed and we now uses
s_csum_seed every time for the xattr block csum. The corresponding
patch for the e2fsprogs will be sent in another patch.

This is spotted by xfstests 117.

Signed-off-by: Tao Ma <boyu.mt@...bao.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Acked-by: Darrick J. Wong <djwong@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/xattr.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -127,19 +127,16 @@ static __le32 ext4_xattr_block_csum(stru
 				    struct ext4_xattr_header *hdr)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	struct ext4_inode_info *ei = EXT4_I(inode);
 	__u32 csum, old;

 	old = hdr->h_checksum;
 	hdr->h_checksum = 0;
-	if (le32_to_cpu(hdr->h_refcount) != 1) {
-		block_nr = cpu_to_le64(block_nr);
-		csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
-				   sizeof(block_nr));
-	} else
-		csum = ei->i_csum_seed;
+	block_nr = cpu_to_le64(block_nr);
+	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&block_nr,
+			   sizeof(block_nr));
 	csum = ext4_chksum(sbi, csum, (__u8 *)hdr,
 			   EXT4_BLOCK_SIZE(inode->i_sb));
+
 	hdr->h_checksum = old;
 	return cpu_to_le32(csum);
 }

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/