lib/blkid: fix unaligned access to hfs_mdb

With -Wall, gcc warns:

      ./probe.c:1209:42: error: taking address of packed member of
               'struct hfs_mdb' may result in an unaligned pointer value

This seems to be a real unaligned memory access bug, as the offset of
the 64-bit value from the start of the buffer is 116, which is not a
multiple of 8.  Fix it by using memcpy().

Do the same for hfsplus to fix the same warning, though in that case the
offset is a multiple of 8 so it was defined behavior.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/blkid/probe.c b/lib/blkid/probe.c
index b8b6558..6a3bb24 100644 (file)
--- a/lib/blkid/probe.c
+++ b/lib/blkid/probe.c
@@ -1198,7 +1198,6 @@ static int probe_hfs(struct blkid_probe *probe __BLKID_ATTR((unused)),
                         unsigned char *buf)
 {
        struct hfs_mdb *hfs = (struct hfs_mdb *)buf;
-       unsigned long long *uuid_ptr;
        char    uuid_str[17];
        __u64   uuid;
 
@@ -1206,8 +1205,8 @@ static int probe_hfs(struct blkid_probe *probe __BLKID_ATTR((unused)),
            (memcmp(hfs->embed_sig, "HX", 2) == 0))
                return 1;       /* Not hfs, but an embedded HFS+ */
 
-       uuid_ptr = (unsigned long long *)hfs->finder_info.id;
-       uuid = blkid_le64(*uuid_ptr);
+       memcpy(&uuid, hfs->finder_info.id, 8);
+       uuid = blkid_le64(uuid);
        if (uuid) {
                sprintf(uuid_str, "%016llX", uuid);
                blkid_set_tag(probe->dev, "UUID", uuid_str, 0);
@@ -1243,7 +1242,6 @@ static int probe_hfsplus(struct blkid_probe *probe,
        unsigned int leaf_node_size;
        unsigned int leaf_block;
        unsigned int label_len;
-       unsigned long long *uuid_ptr;
        __u64 leaf_off, uuid;
        char    uuid_str[17], label[512];
        int ext;
@@ -1274,8 +1272,8 @@ static int probe_hfsplus(struct blkid_probe *probe,
            (memcmp(hfsplus->signature, "HX", 2) != 0))
                return 1;
 
-       uuid_ptr = (unsigned long long *)hfsplus->finder_info.id;
-       uuid = blkid_le64(*uuid_ptr);
+       memcpy(&uuid, hfsplus->finder_info.id, 8);
+       uuid = blkid_le64(uuid);
        if (uuid) {
                sprintf(uuid_str, "%016llX", uuid);
                blkid_set_tag(probe->dev, "UUID", uuid_str, 0);