resolv: Fix a few unaligned accesses to fields in HEADER

After refactoring the alloca usage in 40c0add7d4 ("resolve: Remove
__res_context_query alloca usage") a few unaligned accesses to HEADER
fields surfaced. These unaligned accesses led to problems when running
the resolv test suite on sparc32-linux (leon) as many tests failed due to
SIGBUS crashes.

The issue(s) occured during T_QUERY_A_AND_AAAA queries as the second query
now can start on an unaligned address (previously it was explicitly aligned).

With this patch the unaligned accesses are now fixed by using the
UHEADER instead to ensure the fields are accessed with byte
loads/stores.

The patch has been verfied by running the resolv test suite on sparc32
and x86_64.

Signed-off-by: Ludwig Rydberg <ludwig.rydberg@gaisler.com>
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>

diff --git a/resolv/res_mkquery.c b/resolv/res_mkquery.c
index e9316b3c37721f54bbc989ca8d3023710777a3dc..a46a92432b501213c194083172c92dfe1bf5d58a 100644 (file)
--- a/resolv/res_mkquery.c
+++ b/resolv/res_mkquery.c
@@ -100,7 +100,7 @@ __res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
                        int class, int type, const unsigned char *data,
                        unsigned char *buf, int buflen)
 {
-  HEADER *hp;
+  UHEADER *hp;
   unsigned char *cp;
   int n;
   unsigned char *dnptrs[20], **dpp, **lastdnptr;
@@ -112,7 +112,7 @@ __res_context_mkquery (struct resolv_context *ctx, int op, const char *dname,
   if ((buf == NULL) || (buflen < HFIXEDSZ))
     return -1;
   memset (buf, 0, HFIXEDSZ);
-  hp = (HEADER *) buf;
+  hp = (UHEADER *) buf;
   /* We randomize the IDs every time.  The old code just incremented
      by one after the initial randomization which still predictable if
      the application does multiple requests.  */
@@ -250,7 +250,7 @@ __res_nopt (struct resolv_context *ctx,
             int n0, unsigned char *buf, int buflen, int anslen)
 {
   uint16_t flags = 0;
-  HEADER *hp = (HEADER *) buf;
+  UHEADER *hp = (UHEADER *) buf;
   unsigned char *cp = buf + n0;
   unsigned char *ep = buf + buflen;
 

diff --git a/resolv/res_queriesmatch.c b/resolv/res_queriesmatch.c
index ba1c1d0c0cf6cbf66599e45849b99b8890919fe1..37db01a1b048ec5d344395f69ff8836bc9ae994e 100644 (file)
--- a/resolv/res_queriesmatch.c
+++ b/resolv/res_queriesmatch.c
@@ -95,14 +95,14 @@ __libc_res_queriesmatch (const unsigned char *buf1, const unsigned char *eom1,
 
   /* Only header section present in replies to dynamic update
      packets.  */
-  if ((((HEADER *) buf1)->opcode == ns_o_update) &&
-      (((HEADER *) buf2)->opcode == ns_o_update))
+  if ((((UHEADER *) buf1)->opcode == ns_o_update) &&
+      (((UHEADER *) buf2)->opcode == ns_o_update))
     return 1;
 
   /* Note that we initially do not convert QDCOUNT to the host byte
      order.  We can compare it with the second buffer's QDCOUNT
      value without doing this.  */
-  int qdcount = ((HEADER *) buf1)->qdcount;
+  int qdcount = ((UHEADER *) buf1)->qdcount;
   if (qdcount != ((UHEADER *) buf2)->qdcount)
     return 0;