libext2fs: enforce the block group descriptor size in ext2fs_open()

Since various parts of the library depend on the value of s_desc_size,
check to make sure it is the correct, expected value based on the file
system features.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index ccf1894..5987185 100644 (file)
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -443,4 +443,7 @@ ec  EXT2_ET_MMP_CHANGE_ABORT,
 ec     EXT2_ET_MMP_OPEN_DIRECT,
        "MMP: open with O_DIRECT failed"
 
+ec     EXT2_ET_BAD_DESC_SIZE,
+       "Block group descriptor size incorrect"
+
        end

diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index 482e4ab..fbe9acd 100644 (file)
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -263,6 +263,21 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
                retval = EXT2_ET_CORRUPT_SUPERBLOCK;
                goto cleanup;
        }
+
+       /* Enforce the block group descriptor size */
+       if (fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) {
+               if (fs->super->s_desc_size != EXT2_MIN_DESC_SIZE_64BIT) {
+                       retval = EXT2_ET_BAD_DESC_SIZE;
+                       goto cleanup;
+               }
+       } else {
+               if (fs->super->s_desc_size &&
+                   fs->super->s_desc_size != EXT2_MIN_DESC_SIZE) {
+                       retval = EXT2_ET_BAD_DESC_SIZE;
+                       goto cleanup;
+               }
+       }
+
        fs->cluster_ratio_bits = fs->super->s_log_cluster_size -
                fs->super->s_log_block_size;
        if (EXT2_BLOCKS_PER_GROUP(fs->super) !=