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>

1 files changed, 3 insertions, 3 deletions

diff --git a/resolv/res_queriesmatch.c b/resolv/res_queriesmatch.c
index ba1c1d0..37db01a 100644
--- 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;