linux-kernel - [PATCH 3.12 37/86] ext4: fix inode checksum calculation problem if i_extra

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Message-Id: <72ac62ba051d86885a6c72af92b0a7dd43c7a8e8.1493888632.git.jslaby@suse.cz>
Date:   Thu,  4 May 2017 11:04:02 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Daeho Jeong <daeho.jeong@...sung.com>,
        Youngjin Gil <youngjin.gil@...sung.com>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        Theodore Ts'o <tytso@....edu>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 37/86] ext4: fix inode checksum calculation problem if i_extra_size is small

From: Daeho Jeong <daeho.jeong@...sung.com>

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

===============

commit 05ac5aa18abd7db341e54df4ae2b4c98ea0e43b7 upstream.

We've fixed the race condition problem in calculating ext4 checksum
value in commit b47820edd163 ("ext4: avoid modifying checksum fields
directly during checksum veficationon"). However, by this change,
when calculating the checksum value of inode whose i_extra_size is
less than 4, we couldn't calculate the checksum value in a proper way.
This problem was found and reported by Nix, Thank you.

Reported-by: Nix <nix@...eri.org.uk>
Signed-off-by: Daeho Jeong <daeho.jeong@...sung.com>
Signed-off-by: Youngjin Gil <youngjin.gil@...sung.com>
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 fs/ext4/inode.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 50fc2d1da9a9..9a3e7cffd6eb 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -73,10 +73,9 @@ static __u32 ext4_inode_csum(struct inode *inode, struct ext4_inode *raw,
 			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);
 		}
+		csum = ext4_chksum(sbi, csum, (__u8 *)raw + offset,
+				   EXT4_INODE_SIZE(inode->i_sb) - offset);
 	}
 
 	return csum;
-- 
2.12.2