libblkid: btrfs: add checksum support

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>

diff --git a/libblkid/src/superblocks/btrfs.c b/libblkid/src/superblocks/btrfs.c
index 6e3fb71e40b42f5394fb7ca8fd527229ce9c6c51..249341808674049a8de6e8f5f251b9bc056fedeb 100644 (file)
--- a/libblkid/src/superblocks/btrfs.c
+++ b/libblkid/src/superblocks/btrfs.c
@@ -18,9 +18,15 @@
 #endif
 
 #include "superblocks.h"
+#include "crc32c.h"
+
+union btrfs_super_block_csum {
+       uint8_t bytes[32];
+       uint32_t crc32c;
+};
 
 struct btrfs_super_block {
-       uint8_t csum[32];
+       union btrfs_super_block_csum csum;
        uint8_t fsid[16];
        uint64_t bytenr;
        uint64_t flags;
@@ -64,6 +70,7 @@ struct btrfs_super_block {
                uint8_t fsid[16];
        } __attribute__ ((__packed__)) dev_item;
        uint8_t label[256];
+       uint8_t padding[3541]; /* pad to BTRFS_SUPER_INFO_SIZE for csum calculation */
 } __attribute__ ((__packed__));
 
 #define BTRFS_SUPER_INFO_SIZE 4096
@@ -202,6 +209,21 @@ out:
 }
 #endif
 
+static int btrfs_verify_csum(blkid_probe pr, const struct btrfs_super_block *bfs)
+{
+       int csum_type = le16_to_cpu(bfs->csum_type);
+       if (csum_type != 0) {
+               DBG(LOWPROBE, ul_debug("(btrfs) unknown checksum type %d, skipping validation",
+                                      csum_type));
+               return 1;
+       }
+       uint32_t crc = crc32c(~0L, (char *) bfs + sizeof(bfs->csum),
+                       sizeof(*bfs) - sizeof(bfs->csum)
+       );
+       crc ^= ~0L;
+       return blkid_probe_verify_csum(pr, crc, le32_to_cpu(bfs->csum.crc32c));
+}
+
 static int probe_btrfs(blkid_probe pr, const struct blkid_idmag *mag)
 {
        struct btrfs_super_block *bfs;
@@ -227,6 +249,9 @@ static int probe_btrfs(blkid_probe pr, const struct blkid_idmag *mag)
        if (!bfs)
                return errno ? -errno : 1;
 
+       if (!btrfs_verify_csum(pr, bfs))
+               return 1;
+
        if (*bfs->label)
                blkid_probe_set_label(pr,
                                (unsigned char *) bfs->label,