libblkid: ext: add checksum support

diff --git a/libblkid/src/superblocks/ext.c b/libblkid/src/superblocks/ext.c
index 1c799429e5cf41b32fc39fd271f6f06ab2a3160d..885fec270a7cb02180a9bbca5a5fdaf3cc40bfdc 100644 (file)
--- a/libblkid/src/superblocks/ext.c
+++ b/libblkid/src/superblocks/ext.c
@@ -19,6 +19,7 @@
 #include <time.h>
 
 #include "superblocks.h"
+#include "crc32c.h"
 
 struct ext2_super_block {
        uint32_t                s_inodes_count;
@@ -74,7 +75,8 @@ struct ext2_super_block {
        uint16_t                s_mmp_interval;
        uint64_t                s_mmp_block;
        uint32_t                s_raid_stripe_width;
-       uint32_t                s_reserved[163];
+       uint32_t                s_reserved[162];
+       uint32_t                s_checksum;
 } __attribute__((packed));
 
 /* magic string */
@@ -102,6 +104,7 @@ struct ext2_super_block {
 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM                0x0010
 #define EXT4_FEATURE_RO_COMPAT_DIR_NLINK       0x0020
 #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE     0x0040
+#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM   0x0400
 
 /* for s_feature_incompat */
 #define EXT2_FEATURE_INCOMPAT_FILETYPE         0x0002
@@ -148,9 +151,14 @@ static struct ext2_super_block *ext_get_super(
        struct ext2_super_block *es;
 
        es = (struct ext2_super_block *)
-                       blkid_probe_get_buffer(pr, EXT_SB_OFF, 0x200);
+                       blkid_probe_get_buffer(pr, EXT_SB_OFF, sizeof(struct ext2_super_block));
        if (!es)
                return NULL;
+       if (le32_to_cpu(es->s_feature_ro_compat) & EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) {
+               uint32_t csum = crc32c(~0, es, offsetof(struct ext2_super_block, s_checksum));
+               if (!blkid_probe_verify_csum(pr, csum, le32_to_cpu(es->s_checksum)))
+                       return NULL;
+       }
        if (fc)
                *fc = le32_to_cpu(es->s_feature_compat);
        if (fi)