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resolv: Fix a few unaligned accesses to fields in HEADER

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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>
This commit is contained in:
Ludwig Rydberg 2023-12-11 13:50:41 +01:00 committed by Florian Weimer
parent 4753e92868
commit fc039ce850
2 changed files with 6 additions and 6 deletions
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6
resolv/res_mkquery.c
View File

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

6
resolv/res_queriesmatch.c
View File

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