libblkid: (zonefs) avoid modifying shared buffer

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

diff --git a/libblkid/src/superblocks/zonefs.c b/libblkid/src/superblocks/zonefs.c
index b18dc2c6deb7bcda8a24a4535f9dbd94d4b3a9cc..8aa45b0d34b3e04faad504a9b46e0c771fb25138 100644 (file)
--- a/libblkid/src/superblocks/zonefs.c
+++ b/libblkid/src/superblocks/zonefs.c
@@ -49,18 +49,19 @@ struct zonefs_super {
 
 } __attribute__ ((packed));
 
-static int zonefs_verify_csum(blkid_probe pr, struct zonefs_super *sb)
+static int zonefs_verify_csum(blkid_probe pr, const struct zonefs_super *sb)
 {
        uint32_t expected = le32_to_cpu(sb->s_crc);
-       sb->s_crc = 0;
-       uint32_t crc = ul_crc32(~0LL, (unsigned char *) sb, sizeof(*sb));
+       uint32_t crc = ul_crc32_exclude_offset(
+                       ~0LL, (unsigned char *) sb, sizeof(*sb),
+                      offsetof(typeof(*sb), s_crc), sizeof(sb->s_crc));
        return blkid_probe_verify_csum(pr, crc, expected);
 }
 
 static int probe_zonefs(blkid_probe pr,
                const struct blkid_idmag *mag  __attribute__((__unused__)))
 {
-       struct zonefs_super *sb;
+       const struct zonefs_super *sb;
 
        sb = (struct zonefs_super *)
                blkid_probe_get_buffer(pr, ZONEFS_SB_OFST,