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authorDarrick J. Wong <djwong@us.ibm.com>2012-04-30 02:47:10 +0400
committerTheodore Ts'o <tytso@mit.edu>2012-04-30 02:47:10 +0400
commit5c359a47e7d999a0ea7f397da2c15590d0a82815 (patch)
treef104bbabd12d6ac422bf80a6c477b803102ed3c7 /fs/ext4
parentfeb0ab32a57e4e6c8b24f6fb68f0ce08efe4603c (diff)
downloadlinux-5c359a47e7d999a0ea7f397da2c15590d0a82815.tar.xz
ext4: add checksums to the MMP block
Compute and verify a checksum for the MMP block. Signed-off-by: Darrick J. Wong <djwong@us.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4')
-rw-r--r--fs/ext4/ext4.h3
-rw-r--r--fs/ext4/mmp.c44
2 files changed, 42 insertions, 5 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 84e76bb96070..0ee9669394f5 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2413,6 +2413,9 @@ extern int ext4_bio_write_page(struct ext4_io_submit *io,
/* mmp.c */
extern int ext4_multi_mount_protect(struct super_block *, ext4_fsblk_t);
+extern void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp);
+extern int ext4_mmp_csum_verify(struct super_block *sb,
+ struct mmp_struct *mmp);
/* BH_Uninit flag: blocks are allocated but uninitialized on disk */
enum ext4_state_bits {
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index ed6548d89165..f99a1311e847 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -6,12 +6,45 @@
#include "ext4.h"
+/* Checksumming functions */
+static __u32 ext4_mmp_csum(struct super_block *sb, struct mmp_struct *mmp)
+{
+ struct ext4_sb_info *sbi = EXT4_SB(sb);
+ int offset = offsetof(struct mmp_struct, mmp_checksum);
+ __u32 csum;
+
+ csum = ext4_chksum(sbi, sbi->s_csum_seed, (char *)mmp, offset);
+
+ return cpu_to_le32(csum);
+}
+
+int ext4_mmp_csum_verify(struct super_block *sb, struct mmp_struct *mmp)
+{
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return 1;
+
+ return mmp->mmp_checksum == ext4_mmp_csum(sb, mmp);
+}
+
+void ext4_mmp_csum_set(struct super_block *sb, struct mmp_struct *mmp)
+{
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return;
+
+ mmp->mmp_checksum = ext4_mmp_csum(sb, mmp);
+}
+
/*
* Write the MMP block using WRITE_SYNC to try to get the block on-disk
* faster.
*/
-static int write_mmp_block(struct buffer_head *bh)
+static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
{
+ struct mmp_struct *mmp = (struct mmp_struct *)(bh->b_data);
+
+ ext4_mmp_csum_set(sb, mmp);
mark_buffer_dirty(bh);
lock_buffer(bh);
bh->b_end_io = end_buffer_write_sync;
@@ -59,7 +92,8 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
}
mmp = (struct mmp_struct *)((*bh)->b_data);
- if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC)
+ if (le32_to_cpu(mmp->mmp_magic) != EXT4_MMP_MAGIC ||
+ !ext4_mmp_csum_verify(sb, mmp))
return -EINVAL;
return 0;
@@ -120,7 +154,7 @@ static int kmmpd(void *data)
mmp->mmp_time = cpu_to_le64(get_seconds());
last_update_time = jiffies;
- retval = write_mmp_block(bh);
+ retval = write_mmp_block(sb, bh);
/*
* Don't spew too many error messages. Print one every
* (s_mmp_update_interval * 60) seconds.
@@ -200,7 +234,7 @@ static int kmmpd(void *data)
mmp->mmp_seq = cpu_to_le32(EXT4_MMP_SEQ_CLEAN);
mmp->mmp_time = cpu_to_le64(get_seconds());
- retval = write_mmp_block(bh);
+ retval = write_mmp_block(sb, bh);
failed:
kfree(data);
@@ -299,7 +333,7 @@ skip:
seq = mmp_new_seq();
mmp->mmp_seq = cpu_to_le32(seq);
- retval = write_mmp_block(bh);
+ retval = write_mmp_block(sb, bh);
if (retval)
goto failed;