Fix bus error when accessing MBR partition records

Since the MBR layout only has partition records as 2-byte aligned, the
32-bit fields in them are not aligned. Thus, they cannot be accessed on
some architectures (such as SPARC) by using a "struct MBR_part_record *"
pointer, as the compiler can assume that the pointer is properly aligned.
Instead, the records must be accessed by going through the MBR struct
itself every time.

Signed-off-by: James Clarke <jrtc27@jrtc27.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>

diff --git a/part.h b/part.h
index 862a14c32896da732a6b73f285614a2d2c5a21a8..e697fb4684917bda9eac64df7cdff0348f2e133b 100644 (file)
--- a/part.h
+++ b/part.h
@@ -40,7 +40,7 @@ struct MBR_part_record {
   __u8 last_cyl;
   __u32 first_sect_lba;
   __u32 blocks_num;
-};
+} __attribute__((packed));
 
 struct MBR {
        __u8 pad[446];

diff --git a/super-mbr.c b/super-mbr.c
index 62b3f03126cbda2a3a19af14cb123f2646cfff7f..f5e4ceabbfbab24135bc37c64bf08e2c50881fbe 100644 (file)
--- a/super-mbr.c
+++ b/super-mbr.c
@@ -57,6 +57,11 @@ static void examine_mbr(struct supertype *st, char *homehost)
 
        printf("   MBR Magic : %04x\n", sb->magic);
        for (i = 0; i < MBR_PARTITIONS; i++)
+               /*
+                * Have to make every access through sb rather than using a
+                * pointer to the partition table (or an entry), since the
+                * entries are not properly aligned.
+                */
                if (sb->parts[i].blocks_num)
                        printf("Partition[%d] : %12lu sectors at %12lu (type %02x)\n",
                               i,
@@ -151,6 +156,11 @@ static void getinfo_mbr(struct supertype *st, struct mdinfo *info, char *map)
        info->component_size = 0;
 
        for (i = 0; i < MBR_PARTITIONS ; i++)
+               /*
+                * Have to make every access through sb rather than using a
+                * pointer to the partition table (or an entry), since the
+                * entries are not properly aligned.
+                */
                if (sb->parts[i].blocks_num) {
                        unsigned long last =
                                (unsigned long)__le32_to_cpu(sb->parts[i].blocks_num)

diff --git a/util.c b/util.c
index a238a2107b968443ad530506340cfed7e21f8ef3..9e4718fd988c8ed7de7ec3745deb480e75042f67 100644 (file)
--- a/util.c
+++ b/util.c
@@ -1412,7 +1412,6 @@ static int get_gpt_last_partition_end(int fd, unsigned long long *endofpart)
 static int get_last_partition_end(int fd, unsigned long long *endofpart)
 {
        struct MBR boot_sect;
-       struct MBR_part_record *part;
        unsigned long long curr_part_end;
        unsigned part_nr;
        int retval = 0;
@@ -1429,21 +1428,26 @@ static int get_last_partition_end(int fd, unsigned long long *endofpart)
        if (boot_sect.magic == MBR_SIGNATURE_MAGIC) {
                retval = 1;
                /* found the correct signature */
-               part = boot_sect.parts;
 
                for (part_nr = 0; part_nr < MBR_PARTITIONS; part_nr++) {
+                       /*
+                        * Have to make every access through boot_sect rather
+                        * than using a pointer to the partition table (or an
+                        * entry), since the entries are not properly aligned.
+                        */
+
                        /* check for GPT type */
-                       if (part->part_type == MBR_GPT_PARTITION_TYPE) {
+                       if (boot_sect.parts[part_nr].part_type ==
+                           MBR_GPT_PARTITION_TYPE) {
                                retval = get_gpt_last_partition_end(fd, endofpart);
                                break;
                        }
                        /* check the last used lba for the current partition  */
-                       curr_part_end = __le32_to_cpu(part->first_sect_lba) +
-                               __le32_to_cpu(part->blocks_num);
+                       curr_part_end =
+                               __le32_to_cpu(boot_sect.parts[part_nr].first_sect_lba) +
+                               __le32_to_cpu(boot_sect.parts[part_nr].blocks_num);
                        if (curr_part_end > *endofpart)
                                *endofpart = curr_part_end;
-
-                       part++;
                }
        } else {
                /* Unknown partition table */