Don' use unalligned pointers, this is undefined behaviour.

diff --git a/kpartx/dos.c b/kpartx/dos.c
index ae8ecba..60a6bfd 100644 (file)
--- a/kpartx/dos.c
+++ b/kpartx/dos.c
@@ -1,6 +1,7 @@
 #include "kpartx.h"
 #include "byteorder.h"
 #include <stdio.h>
+#include <string.h>
 #include "dos.h"
 
 static int
@@ -12,7 +13,7 @@ static int
 read_extended_partition(int fd, struct partition *ep,
                        struct slice *sp, int ns)
 {
-       struct partition *p;
+       struct partition p;
        unsigned long start, here;
        unsigned char *bp;
        int loopct = 0;
@@ -33,14 +34,13 @@ read_extended_partition(int fd, struct partition *ep,
                if (bp[510] != 0x55 || bp[511] != 0xaa)
                        return n;
 
-               p = (struct partition *) (bp + 0x1be);
-
-               for (i=0; i<2; i++, p++) {
-                       if (p->nr_sects == 0 || is_extended(p->sys_type))
+               for (i=0; i<2; i++) {
+                       memcpy(&p, bp + 0x1be + i * sizeof (p), sizeof (p));
+                       if (p.nr_sects == 0 || is_extended(p.sys_type))
                                continue;
                        if (n < ns) {
-                               sp[n].start = here + le32_to_cpu(p->start_sect);
-                               sp[n].size = le32_to_cpu(p->nr_sects);
+                               sp[n].start = here + le32_to_cpu(p.start_sect);
+                               sp[n].size = le32_to_cpu(p.nr_sects);
                                n++;
                        } else {
                                fprintf(stderr,
@@ -50,10 +50,10 @@ read_extended_partition(int fd, struct partition *ep,
                        loopct = 0;
                }
 
-               p -= 2;
-               for (i=0; i<2; i++, p++) {
-                       if(p->nr_sects != 0 && is_extended(p->sys_type)) {
-                               here = start + le32_to_cpu(p->start_sect);
+               for (i=0; i<2; i++) {
+                       memcpy(&p, bp + 0x1be + i * sizeof (p), sizeof (p));
+                       if(p.nr_sects != 0 && is_extended(p.sys_type)) {
+                               here = start + le32_to_cpu(p.start_sect);
                                moretodo = 1;
                                break;
                        }
@@ -69,7 +69,7 @@ is_gpt(int type) {
 
 int
 read_dos_pt(int fd, struct slice all, struct slice *sp, int ns) {
-       struct partition *p;
+       struct partition p;
        unsigned long offset = all.start;
        int i, n=0;
        unsigned char *bp;
@@ -81,32 +81,29 @@ read_dos_pt(int fd, struct slice all, struct slice *sp, int ns) {
        if (bp[510] != 0x55 || bp[511] != 0xaa)
                return -1;
 
-       p = (struct partition *) (bp + 0x1be);
        for (i=0; i<4; i++) {
-               if (is_gpt(p->sys_type)) {
+               memcpy(&p, bp + 0x1be + i * sizeof (p), sizeof (p));
+               if (is_gpt(p.sys_type)) {
                        return 0;
                }
-               p++;
        }
-       p = (struct partition *) (bp + 0x1be);
        for (i=0; i<4; i++) {
+               memcpy(&p, bp + 0x1be + i * sizeof (p), sizeof (p));
                /* always add, even if zero length */
                if (n < ns) {
-                       sp[n].start =  le32_to_cpu(p->start_sect);
-                       sp[n].size = le32_to_cpu(p->nr_sects);
+                       sp[n].start =  le32_to_cpu(p.start_sect);
+                       sp[n].size = le32_to_cpu(p.nr_sects);
                        n++;
                } else {
                        fprintf(stderr,
                                "dos_partition: too many slices\n");
                        break;
                }
-               p++;
        }
-       p = (struct partition *) (bp + 0x1be);
        for (i=0; i<4; i++) {
-               if (is_extended(p->sys_type))
-                       n += read_extended_partition(fd, p, sp+n, ns-n);
-               p++;
+               memcpy(&p, bp + 0x1be + i * sizeof (p), sizeof (p));
+               if (is_extended(p.sys_type))
+                       n += read_extended_partition(fd, &p, sp+n, ns-n);
        }
        return n;
 }