libblkid: (xfs) cleanup checksum code

* move variables definition to the begin of the block
* check blkid_probe_get_sb_buffer() result [detected by coverity scan]

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libblkid/src/superblocks/xfs.c b/libblkid/src/superblocks/xfs.c
index 26a238fb4d7a9d9f086c50487acf696ff82f9058..b26b960d277fed84fa487bafb469000df2d938bb 100644 (file)
--- a/libblkid/src/superblocks/xfs.c
+++ b/libblkid/src/superblocks/xfs.c
@@ -205,16 +205,23 @@ static int xfs_verify_sb(struct xfs_super_block *ondisk, blkid_probe pr,
                return 0;
 
        if ((sbp->sb_versionnum & 0x0f) == 5) {
+               uint32_t expected, crc;
+               unsigned char *csummed;
+
                if (!(sbp->sb_versionnum | XFS_SB_VERSION_MOREBITSBIT))
                        return 0;
                if (!(sbp->sb_features2 | XFS_SB_VERSION2_CRCBIT))
                        return 0;
-               uint32_t expected = sbp->sb_crc;
-               unsigned char *csummed = blkid_probe_get_sb_buffer(
-                               pr, mag, sbp->sb_sectsize);
+
+               expected = sbp->sb_crc;
+               csummed = blkid_probe_get_sb_buffer(pr, mag, sbp->sb_sectsize);
+               if (!csummed)
+                       return 0;
+
                ondisk->sb_crc = 0;
-               uint32_t crc = crc32c(~0LL, csummed, sbp->sb_sectsize);
+               crc = crc32c(~0LL, csummed, sbp->sb_sectsize);
                crc = bswap_32(crc ^ ~0LL);
+
                if (!blkid_probe_verify_csum(pr, crc, expected))
                        return 0;
        }