[31/54] libext2fs: Calculate and verify superblock checksums

diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c
index 1867be3..a0e28ba 100644
--- a/lib/ext2fs/closefs.c
+++ b/lib/ext2fs/closefs.c
@@ -246,15 +246,19 @@  static errcode_t write_backup_super(ext2_filsys fs, dgrp_t group,
 				    blk_t group_block,
 				    struct ext2_super_block *super_shadow)
 {
+	errcode_t retval;
 	dgrp_t	sgrp = group;
 
 	if (sgrp > ((1 << 16) - 1))
 		sgrp = (1 << 16) - 1;
+
+	super_shadow->s_block_group_nr = sgrp;
 #ifdef WORDS_BIGENDIAN
-	super_shadow->s_block_group_nr = ext2fs_swab16(sgrp);
-#else
-	fs->super->s_block_group_nr = sgrp;
+	ext2fs_swap_super(super_shadow);
 #endif
+	retval = ext2fs_superblock_csum_set(fs, super_shadow);
+	if (retval)
+		return retval;
 
 	return io_channel_write_blk64(fs->io, group_block, -SUPERBLOCK_SIZE,
 				    super_shadow);
@@ -314,6 +318,7 @@  errcode_t ext2fs_flush2(ext2_filsys fs, int flags)
 				  &group_shadow);
 	if (retval)
 		goto errout;
+	memcpy(super_shadow, fs->super, sizeof(struct ext2_super_block));
 	memcpy(group_shadow, fs->group_desc, (size_t) fs->blocksize *
 	       fs->desc_blocks);
 
@@ -334,10 +339,6 @@  errcode_t ext2fs_flush2(ext2_filsys fs, int flags)
 	 */
 	fs->super->s_state &= ~EXT2_VALID_FS;
 	fs->super->s_feature_incompat &= ~EXT3_FEATURE_INCOMPAT_RECOVER;
-#ifdef WORDS_BIGENDIAN
-	*super_shadow = *fs->super;
-	ext2fs_swap_super(super_shadow);
-#endif
 
 	/*
 	 * If this is an external journal device, don't write out the
@@ -412,6 +413,10 @@  write_primary_superblock_only:
 	ext2fs_swap_super(super_shadow);
 #endif
 
+	retval = ext2fs_superblock_csum_set(fs, super_shadow);
+	if (retval)
+		return retval;
+
 	if (!(flags & EXT2_FLAG_FLUSH_NO_SYNC))
 		retval = io_channel_flush(fs->io);
 	retval = write_primary_superblock(fs, super_shadow);
diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
index 46f0cb5..4d01bcd 100644
--- a/lib/ext2fs/csum.c
+++ b/lib/ext2fs/csum.c
@@ -30,6 +30,41 @@ 
 #define STATIC static
 #endif
 
+static __u32 ext2fs_superblock_csum(ext2_filsys fs, struct ext2_super_block *sb)
+{
+	int offset = offsetof(struct ext2_super_block, s_checksum);
+
+	return ext2fs_crc32c_le(~0, (unsigned char *)sb, offset);
+}
+
+int ext2fs_superblock_csum_verify(ext2_filsys fs, struct ext2_super_block *sb)
+{
+	__u32 calculated;
+
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 1;
+
+	calculated = ext2fs_superblock_csum(fs, sb);
+
+	return ext2fs_le32_to_cpu(sb->s_checksum) == calculated;
+}
+
+errcode_t ext2fs_superblock_csum_set(ext2_filsys fs,
+				     struct ext2_super_block *sb)
+{
+	__u32 crc;
+
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+		EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 0;
+
+	crc = ext2fs_superblock_csum(fs, sb);
+	sb->s_checksum = ext2fs_cpu_to_le32(crc);
+
+	return 0;
+}
+
 static errcode_t ext2fs_ext_attr_block_csum(ext2_filsys fs, ext2_ino_t inum,
 					    blk64_t block,
 					    struct ext2_ext_attr_header *hdr,
diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index 177a97f..0fab4e0 100644
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -461,4 +461,7 @@  ec	EXT2_ET_DIR_CSUM_INVALID,
 ec	EXT2_ET_EXT_ATTR_CSUM_INVALID,
 	"Extended attribute block checksum does not match block"
 
+ec	EXT2_ET_SB_CSUM_INVALID,
+	"Superblock checksum does not match superblock"
+
 	end
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 5684df5..3c52f4b 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -952,6 +952,10 @@  extern __u32 ext2fs_crc32c_be(__u32 crc, unsigned char const *p, size_t len);
 extern __u32 ext2fs_crc32c_le(__u32 crc, unsigned char const *p, size_t len);
 
 /* csum.c */
+extern errcode_t ext2fs_superblock_csum_set(ext2_filsys fs,
+					    struct ext2_super_block *sb);
+extern int ext2fs_superblock_csum_verify(ext2_filsys fs,
+					 struct ext2_super_block *sb);
 extern errcode_t ext2fs_ext_attr_block_csum_set(ext2_filsys fs,
 					ext2_ino_t inum, blk64_t block,
 					struct ext2_ext_attr_header *hdr);
diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index 10beb06..8b7e750 100644
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -193,6 +193,12 @@  errcode_t ext2fs_open2(const char *name, const char *io_options,
 	if (fs->orig_super)
 		memcpy(fs->orig_super, fs->super, SUPERBLOCK_SIZE);
 
+	if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+	    !ext2fs_superblock_csum_verify(fs, fs->super)) {
+		retval = EXT2_ET_SB_CSUM_INVALID;
+		goto cleanup;
+	}
+
 #ifdef WORDS_BIGENDIAN
 	fs->flags |= EXT2_FLAG_SWAP_BYTES;
 	ext2fs_swap_super(fs->super);