libext2fs: add checksum to MMP block

Calculate and verify a checksum of the MMP block.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index c3f03e3..aec61ab 100644 (file)
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -2250,6 +2250,7 @@ void do_dump_mmp(int argc EXT2FS_ATTR((unused)), char *argv[])
        fprintf(stdout, "node_name: %s\n", mmp_s->mmp_nodename);
        fprintf(stdout, "device_name: %s\n", mmp_s->mmp_bdevname);
        fprintf(stdout, "magic: 0x%x\n", mmp_s->mmp_magic);
+       fprintf(stdout, "checksum: 0x%08x\n", mmp_s->mmp_checksum);
 #else
        fprintf(stdout, "MMP is unsupported, please recompile with "
                        "--enable-mmp\n");

diff --git a/debugfs/set_fields.c b/debugfs/set_fields.c
index 4126e7b..fac95a6 100644 (file)
--- a/debugfs/set_fields.c
+++ b/debugfs/set_fields.c
@@ -256,6 +256,7 @@ static struct field_set_info mmp_fields[] = {
        { "bdevname", &set_mmp.mmp_bdevname, NULL, sizeof(set_mmp.mmp_bdevname),
                parse_string },
        { "check_interval", &set_mmp.mmp_check_interval, NULL, 2, parse_uint },
+       { "checksum", &set_mmp.mmp_checksum, NULL, 4, parse_uint },
 };
 
 static int check_suffix(const char *field)

diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
index 7f5d779..3083fb1 100644 (file)
--- a/lib/ext2fs/csum.c
+++ b/lib/ext2fs/csum.c
@@ -30,6 +30,40 @@
 #define STATIC static
 #endif
 
+static __u32 ext2fs_mmp_csum(ext2_filsys fs, struct mmp_struct *mmp)
+{
+       int offset = offsetof(struct mmp_struct, mmp_checksum);
+
+       return ext2fs_crc32c_le(fs->csum_seed, (unsigned char *)mmp, offset);
+}
+
+int ext2fs_mmp_csum_verify(ext2_filsys fs, struct mmp_struct *mmp)
+{
+       __u32 calculated;
+
+       if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+                                       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+               return 1;
+
+       calculated = ext2fs_mmp_csum(fs, mmp);
+
+       return ext2fs_le32_to_cpu(mmp->mmp_checksum) == calculated;
+}
+
+errcode_t ext2fs_mmp_csum_set(ext2_filsys fs, struct mmp_struct *mmp)
+{
+       __u32 crc;
+
+       if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+               EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+               return 0;
+
+       crc = ext2fs_mmp_csum(fs, mmp);
+       mmp->mmp_checksum = ext2fs_cpu_to_le32(crc);
+
+       return 0;
+}
+
 int ext2fs_verify_csum_type(ext2_filsys fs, struct ext2_super_block *sb)
 {
        if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,

diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index cb63689..c99a167 100644 (file)
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -470,4 +470,7 @@ ec  EXT2_ET_SB_CSUM_INVALID,
 ec     EXT2_ET_UNKNOWN_CSUM,
        "Unknown checksum algorithm"
 
+ec     EXT2_ET_MMP_CSUM_INVALID,
+       "MMP block checksum does not match MMP block"
+
        end

diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 9d88b89..7e0253d 100644 (file)
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -949,6 +949,8 @@ 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_mmp_csum_set(ext2_filsys fs, struct mmp_struct *mmp);
+extern int ext2fs_mmp_csum_verify(ext2_filsys, struct mmp_struct *mmp);
 extern int ext2fs_verify_csum_type(ext2_filsys fs, struct ext2_super_block *sb);
 extern errcode_t ext2fs_superblock_csum_set(ext2_filsys fs,
                                            struct ext2_super_block *sb);
@@ -1444,6 +1446,7 @@ errcode_t ext2fs_mmp_clear(ext2_filsys fs);
 errcode_t ext2fs_mmp_init(ext2_filsys fs);
 errcode_t ext2fs_mmp_start(ext2_filsys fs);
 errcode_t ext2fs_mmp_update(ext2_filsys fs);
+errcode_t ext2fs_mmp_update2(ext2_filsys fs, int immediately);
 errcode_t ext2fs_mmp_stop(ext2_filsys fs);
 unsigned ext2fs_mmp_new_seq(void);
 

diff --git a/lib/ext2fs/mmp.c b/lib/ext2fs/mmp.c
index c76aefa..10fb68a 100644 (file)
--- a/lib/ext2fs/mmp.c
+++ b/lib/ext2fs/mmp.c
@@ -75,6 +75,11 @@ errcode_t ext2fs_mmp_read(ext2_filsys fs, blk64_t mmp_blk, void *buf)
        }
 
        mmp_cmp = fs->mmp_cmp;
+
+       if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+           !ext2fs_mmp_csum_verify(fs, mmp_cmp))
+               retval = EXT2_ET_MMP_CSUM_INVALID;
+
 #ifdef WORDS_BIGENDIAN
        ext2fs_swap_mmp(mmp_cmp);
 #endif
@@ -113,6 +118,10 @@ errcode_t ext2fs_mmp_write(ext2_filsys fs, blk64_t mmp_blk, void *buf)
        ext2fs_swap_mmp(mmp_s);
 #endif
 
+       retval = ext2fs_mmp_csum_set(fs, mmp_s);
+       if (retval)
+               return retval;
+
        /* I was tempted to make this use O_DIRECT and the mmp_fd, but
         * this caused no end of grief, while leaving it as-is works. */
        retval = io_channel_write_blk64(fs->io, mmp_blk, -(int)sizeof(struct mmp_struct), buf);
@@ -192,6 +201,11 @@ out:
        return retval;
 }
 
+errcode_t ext2fs_mmp_update(ext2_filsys fs)
+{
+       return ext2fs_mmp_update2(fs, 0);
+}
+
 errcode_t ext2fs_mmp_clear(ext2_filsys fs)
 {
 #ifdef CONFIG_MMP
@@ -392,7 +406,7 @@ mmp_error:
 /*
  * Update the on-disk mmp buffer, after checking that it hasn't been changed.
  */
-errcode_t ext2fs_mmp_update(ext2_filsys fs)
+errcode_t ext2fs_mmp_update2(ext2_filsys fs, int immediately)
 {
 #ifdef CONFIG_MMP
        struct mmp_struct *mmp, *mmp_cmp;
@@ -404,7 +418,8 @@ errcode_t ext2fs_mmp_update(ext2_filsys fs)
                return 0;
 
        gettimeofday(&tv, 0);
-       if (tv.tv_sec - fs->mmp_last_written < EXT2_MIN_MMP_UPDATE_INTERVAL)
+       if (!immediately &&
+           tv.tv_sec - fs->mmp_last_written < EXT2_MIN_MMP_UPDATE_INTERVAL)
                return 0;
 
        retval = ext2fs_mmp_read(fs, fs->super->s_mmp_block, NULL);

diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
index de178a4..1295e81 100644 (file)
--- a/lib/ext2fs/swapfs.c
+++ b/lib/ext2fs/swapfs.c
@@ -349,6 +349,7 @@ void ext2fs_swap_mmp(struct mmp_struct *mmp)
        mmp->mmp_seq = ext2fs_swab32(mmp->mmp_seq);
        mmp->mmp_time = ext2fs_swab64(mmp->mmp_time);
        mmp->mmp_check_interval = ext2fs_swab16(mmp->mmp_check_interval);
+       mmp->mmp_checksum = ext2fs_swab32(mmp->mmp_checksum);
 }
 
 errcode_t ext2fs_dirent_swab_in(ext2_filsys fs, char *buf, int flags)