Properly align buffer when storing pointers.

Properly align buffer address to sizeof(char *) when storing
pointers to strings.

resolves:
https://fedorahosted.org/sssd/ticket/1359

4 files changed, 24 insertions, 11 deletions

diff --git a/src/sss_client/nss_group.c b/src/sss_client/nss_group.c
index a7fb09375..9e259318d 100644
--- a/src/sss_client/nss_group.c
+++ b/src/sss_client/nss_group.c
@@ -233,14 +233,12 @@ static int sss_nss_getgr_readrep(struct sss_nss_gr_rep *pr,
                                   NULL);
     if (ret != EOK) return ret;
 
-    /* Make sure pr->buffer[i+pad] is 32 bit aligned */
-    pad = 0;
-    while((i + pad) % 4) {
-        pad++;
-    }
+    /* Make sure pr->buffer[i+pad] is aligned to sizeof(char *) */
+    pad = PADDING_SIZE(i, char *);
 
     /* now members */
     pr->result->gr_mem = (char **)&(pr->buffer[i+pad]);
+
     ptmem = (sizeof(char *) * (mem_num + 1)) + pad;
     if (ptmem > dlen) {
         return ERANGE; /* not ENOMEM, ERANGE is what glibc looks for */
diff --git a/src/sss_client/nss_mc_group.c b/src/sss_client/nss_mc_group.c
index 5610233ed..fb5e43f84 100644
--- a/src/sss_client/nss_mc_group.c
+++ b/src/sss_client/nss_mc_group.c
@@ -27,6 +27,7 @@
 #include <sys/mman.h>
 #include <time.h>
 #include "nss_mc.h"
+#include "util/util_safealign.h"
 
 struct sss_cli_mc_ctx gr_mc_ctx = { false, -1, 0, NULL, 0, NULL, 0, NULL, 0 };
 
@@ -64,7 +65,14 @@ static errno_t sss_nss_mc_parse_result(struct sss_mc_rec *rec,
 
     /* fill in group */
     result->gr_gid = data->gid;
-    result->gr_mem = (char **)buffer;
+
+    /* The address &buffer[0] must be aligned to sizeof(char *) */
+    if (!IS_ALIGNED(buffer, char *)) {
+        /* The buffer is not properly aligned. */
+        return EFAULT;
+    }
+
+    result->gr_mem = (char **)DISCARD_ALIGN(buffer);
     result->gr_mem[data->members] = NULL;
 
     cookie = NULL;
diff --git a/src/sss_client/nss_services.c b/src/sss_client/nss_services.c
index b40e1fa94..e89e0d2f1 100644
--- a/src/sss_client/nss_services.c
+++ b/src/sss_client/nss_services.c
@@ -127,11 +127,8 @@ sss_nss_getsvc_readrep(struct sss_nss_svc_rep *sr,
                                   NULL);
     if (ret != EOK) return ret;
 
-    /* Make sure sr->buffer[i+pad] is 32-bit aligned */
-    pad = 0;
-    while((i + pad) % 4) {
-        pad++;
-    }
+    /* Make sure sr->buffer[i+pad] is aligned to sizeof(char *) */
+    pad = PADDING_SIZE(i, char *);
 
     /* Copy in the aliases */
     sr->result->s_aliases = (char **) &(sr->buffer[i+pad]);
diff --git a/src/util/util_safealign.h b/src/util/util_safealign.h
index c39ba159b..685d65966 100644
--- a/src/util/util_safealign.h
+++ b/src/util/util_safealign.h
@@ -32,6 +32,16 @@
 #include <string.h>
 #include <stdint.h>
 
+/* Use this macro to suppress alignment warnings (use it
+ * only to suppress false-positives) */
+#define DISCARD_ALIGN(ptr) ((void *)(ptr))
+
+#define IS_ALIGNED(ptr, type) \
+    ((uintptr_t)(ptr) % sizeof(type) == 0)
+
+#define PADDING_SIZE(base, type) \
+    ((sizeof(type) - ((base) % sizeof(type))) % sizeof(type))
+
 #define SIZE_T_OVERFLOW(current, add) \
                         (((size_t)(add)) > (SIZE_MAX - ((size_t)(current))))