1 files changed, 47 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 11a0a7078da7..f80c7e612829 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -122,6 +122,38 @@ static int ext4_verify_csum_type(struct super_block *sb,
         return es->s_checksum_type == EXT4_CRC32C_CHKSUM;
 }
 
+static __le32 ext4_superblock_csum(struct super_block *sb,
+                                   struct ext4_super_block *es)
+{
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+        int offset = offsetof(struct ext4_super_block, s_checksum);
+        __u32 csum;
+
+        csum = ext4_chksum(sbi, ~0, (char *)es, offset);
+
+        return cpu_to_le32(csum);
+}
+
+int ext4_superblock_csum_verify(struct super_block *sb,
+                                struct ext4_super_block *es)
+{
+        if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                return 1;
+
+        return es->s_checksum == ext4_superblock_csum(sb, es);
+}
+
+void ext4_superblock_csum_set(struct super_block *sb,
+                              struct ext4_super_block *es)
+{
+        if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+                EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                return;
+
+        es->s_checksum = ext4_superblock_csum(sb, es);
+}
+
 void *ext4_kvmalloc(size_t size, gfp_t flags)
 {
         void *ret;
@@ -3057,6 +3089,20 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                 }
         }
 
+        /* Check superblock checksum */
+        if (!ext4_superblock_csum_verify(sb, es)) {
+                ext4_msg(sb, KERN_ERR, "VFS: Found ext4 filesystem with "
+                         "invalid superblock checksum.  Run e2fsck?");
+                silent = 1;
+                goto cantfind_ext4;
+        }
+
+        /* Precompute checksum seed for all metadata */
+        if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
+                        EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+                sbi->s_csum_seed = ext4_chksum(sbi, ~0, es->s_uuid,
+                                               sizeof(es->s_uuid));
+
         /* Set defaults before we parse the mount options */
         def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
         set_opt(sb, INIT_INODE_TABLE);
@@ -4059,6 +4105,7 @@ static int ext4_commit_super(struct super_block *sb, int sync)
                                 &EXT4_SB(sb)->s_freeinodes_counter));
         sb->s_dirt = 0;
         BUFFER_TRACE(sbh, "marking dirty");
+        ext4_superblock_csum_set(sb, es);
         mark_buffer_dirty(sbh);
         if (sync) {
                 error = sync_dirty_buffer(sbh);