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resolve: Remove __res_context_query alloca usage
The bufsize on current Linux build is: size_t bufsize = (type == 439963904 ? 2 : 1) * (12 + 4 + 255 + 1); So with upper bound as 544 (2 * (12 + 4 + 255 + 1)). However, it might increase to 2 * PACKETSIZE later with malloc. The default scratch_buffer should fullfill the most usual allocation requirement. Checked on x86_64-linux-gnu and i686-linux-gnu. Reviewed-by: Joe Simmons-Talbott <josimmon@redhat.com>
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@ -80,6 +80,7 @@
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#include <stdlib.h>
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#include <string.h>
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#include <shlib-compat.h>
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#include <scratch_buffer.h>
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#if PACKETSZ > 65536
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#define MAXPACKET PACKETSZ
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@ -114,11 +115,14 @@ __res_context_query (struct resolv_context *ctx, const char *name,
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struct __res_state *statp = ctx->resp;
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UHEADER *hp = (UHEADER *) answer;
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UHEADER *hp2;
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int n, use_malloc = 0;
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int n;
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size_t bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * QUERYSIZE;
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u_char *buf = alloca (bufsize);
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u_char *query1 = buf;
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/* It requires 2 times QUERYSIZE for type == T_QUERY_A_AND_AAAA. */
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struct scratch_buffer buf;
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scratch_buffer_init (&buf);
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_Static_assert (2 * QUERYSIZE <= sizeof (buf.__space.__c),
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"scratch_buffer too small");
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u_char *query1 = buf.data;
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int nquery1 = -1;
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u_char *query2 = NULL;
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int nquery2 = 0;
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@ -129,37 +133,28 @@ __res_context_query (struct resolv_context *ctx, const char *name,
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if (type == T_QUERY_A_AND_AAAA)
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{
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n = __res_context_mkquery (ctx, QUERY, name, class, T_A, NULL,
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query1, bufsize);
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query1, buf.length);
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if (n > 0)
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{
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if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
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{
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/* Use RESOLV_EDNS_BUFFER_SIZE because the receive
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buffer can be reallocated. */
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n = __res_nopt (ctx, n, query1, bufsize,
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n = __res_nopt (ctx, n, query1, buf.length,
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RESOLV_EDNS_BUFFER_SIZE);
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if (n < 0)
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goto unspec_nomem;
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}
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nquery1 = n;
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/* Align the buffer. */
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int npad = ((nquery1 + __alignof__ (HEADER) - 1)
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& ~(__alignof__ (HEADER) - 1)) - nquery1;
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if (n > bufsize - npad)
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{
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n = -1;
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goto unspec_nomem;
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}
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int nused = n + npad;
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query2 = buf + nused;
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query2 = buf.data + n;
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n = __res_context_mkquery (ctx, QUERY, name, class, T_AAAA,
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NULL, query2, bufsize - nused);
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NULL, query2, buf.length - n);
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if (n > 0
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&& (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
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/* Use RESOLV_EDNS_BUFFER_SIZE because the receive
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buffer can be reallocated. */
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n = __res_nopt (ctx, n, query2, bufsize,
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n = __res_nopt (ctx, n, query2, buf.length,
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RESOLV_EDNS_BUFFER_SIZE);
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nquery2 = n;
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}
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@ -169,7 +164,7 @@ __res_context_query (struct resolv_context *ctx, const char *name,
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else
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{
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n = __res_context_mkquery (ctx, QUERY, name, class, type, NULL,
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query1, bufsize);
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query1, buf.length);
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if (n > 0
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&& (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0)
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@ -181,27 +176,25 @@ __res_context_query (struct resolv_context *ctx, const char *name,
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advertise = anslen;
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else
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advertise = RESOLV_EDNS_BUFFER_SIZE;
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n = __res_nopt (ctx, n, query1, bufsize, advertise);
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n = __res_nopt (ctx, n, query1, buf.length, advertise);
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}
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nquery1 = n;
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}
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if (__glibc_unlikely (n <= 0) && !use_malloc) {
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if (__glibc_unlikely (n <= 0)) {
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/* Retry just in case res_nmkquery failed because of too
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short buffer. Shouldn't happen. */
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bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * MAXPACKET;
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buf = malloc (bufsize);
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if (buf != NULL) {
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query1 = buf;
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use_malloc = 1;
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if (scratch_buffer_set_array_size (&buf,
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T_QUERY_A_AND_AAAA ? 2 : 1,
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MAXPACKET)) {
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query1 = buf.data;
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goto again;
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}
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}
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if (__glibc_unlikely (n <= 0)) {
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RES_SET_H_ERRNO(statp, NO_RECOVERY);
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if (use_malloc)
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free (buf);
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scratch_buffer_free (&buf);
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return (n);
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}
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@ -224,8 +217,7 @@ __res_context_query (struct resolv_context *ctx, const char *name,
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answerp2_malloced);
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}
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if (use_malloc)
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free (buf);
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scratch_buffer_free (&buf);
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if (n < 0) {
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RES_SET_H_ERRNO(statp, TRY_AGAIN);
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return (n);
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