[SRU][T][PATCH 1/1] ext4: always initialize the crc32c checksum driver

[Khalid Elmously]

From: Theodore Ts'o <tytso at mit.edu>

CVE-2018-1094

The extended attribute code now uses the crc32c checksum for hashing
purposes, so we should just always always initialize it.  We also want
to prevent NULL pointer dereferences if one of the metadata checksum
features is enabled after the file sytsem is originally mounted.

This issue has been assigned CVE-2018-1094.

https://bugzilla.kernel.org/show_bug.cgi?id=199183
https://bugzilla.redhat.com/show_bug.cgi?id=1560788

Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Cc: stable at vger.kernel.org
(backported from a45403b51582a87872927a3e0fc0a389c26867f1)
Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
---
 fs/ext4/super.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3b313429b83f..26552bf46ca8 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3457,15 +3457,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	}
 
 	/* Load the checksum driver */
-	if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
-				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
-		sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
-		if (IS_ERR(sbi->s_chksum_driver)) {
-			ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
-			ret = PTR_ERR(sbi->s_chksum_driver);
-			sbi->s_chksum_driver = NULL;
-			goto failed_mount;
-		}
+	sbi->s_chksum_driver = crypto_alloc_shash("crc32c", 0, 0);
+	if (IS_ERR(sbi->s_chksum_driver)) {
+		ext4_msg(sb, KERN_ERR, "Cannot load crc32c driver.");
+		ret = PTR_ERR(sbi->s_chksum_driver);
+		sbi->s_chksum_driver = NULL;
+		goto failed_mount;
 	}
 
 	/* Check superblock checksum */
-- 
2.17.1