| Message ID | 20230914175407.2406866-1-adhemerval.zanella@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | resolve: Remove __res_context_query alloca usage | expand |
* Adhemerval Zanella: > @@ -146,20 +150,20 @@ __res_context_query (struct resolv_context *ctx, const char *name, > /* Align the buffer. */ > int npad = ((nquery1 + __alignof__ (HEADER) - 1) > & ~(__alignof__ (HEADER) - 1)) - nquery1; > - if (n > bufsize - npad) > + if (n > buf.length - npad) > { > n = -1; > goto unspec_nomem; > } > int nused = n + npad; The alignment code shouldn't be necessary anymore. Thanks, Florian
On Thu, Sep 14, 2023 at 02:54:07PM -0300, Adhemerval Zanella wrote: > 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. LGTM, Reviewed-by: Joe Simmons-Talbott <josimmon@redhat.com> > --- > resolv/res_query.c | 47 +++++++++++++++++++++++----------------------- > 1 file changed, 24 insertions(+), 23 deletions(-) > > diff --git a/resolv/res_query.c b/resolv/res_query.c > index 049de91b95..b234db83c1 100644 > --- a/resolv/res_query.c > +++ b/resolv/res_query.c > @@ -80,6 +80,7 @@ > #include <stdlib.h> > #include <string.h> > #include <shlib-compat.h> > +#include <scratch_buffer.h> > > #if PACKETSZ > 65536 > #define MAXPACKET PACKETSZ > @@ -114,11 +115,14 @@ __res_context_query (struct resolv_context *ctx, const char *name, > struct __res_state *statp = ctx->resp; > UHEADER *hp = (UHEADER *) answer; > UHEADER *hp2; > - int n, use_malloc = 0; > - > - size_t bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * QUERYSIZE; > - u_char *buf = alloca (bufsize); > - u_char *query1 = buf; > + int n; > + > + /* It requires 2 times QUERYSIZE for type == T_QUERY_A_AND_AAAA. */ > + struct scratch_buffer buf; > + scratch_buffer_init (&buf); > + _Static_assert (2 * QUERYSIZE <= sizeof (buf.__space.__c), > + "scratch_buffer too small"); > + u_char *query1 = buf.data; > int nquery1 = -1; > u_char *query2 = NULL; > int nquery2 = 0; > @@ -129,14 +133,14 @@ __res_context_query (struct resolv_context *ctx, const char *name, > if (type == T_QUERY_A_AND_AAAA) > { > n = __res_context_mkquery (ctx, QUERY, name, class, T_A, NULL, > - query1, bufsize); > + query1, buf.length); > if (n > 0) > { > if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) > { > /* Use RESOLV_EDNS_BUFFER_SIZE because the receive > buffer can be reallocated. */ > - n = __res_nopt (ctx, n, query1, bufsize, > + n = __res_nopt (ctx, n, query1, buf.length, > RESOLV_EDNS_BUFFER_SIZE); > if (n < 0) > goto unspec_nomem; > @@ -146,20 +150,20 @@ __res_context_query (struct resolv_context *ctx, const char *name, > /* Align the buffer. */ > int npad = ((nquery1 + __alignof__ (HEADER) - 1) > & ~(__alignof__ (HEADER) - 1)) - nquery1; > - if (n > bufsize - npad) > + if (n > buf.length - npad) > { > n = -1; > goto unspec_nomem; > } > int nused = n + npad; > - query2 = buf + nused; > + query2 = buf.data + nused; > n = __res_context_mkquery (ctx, QUERY, name, class, T_AAAA, > - NULL, query2, bufsize - nused); > + NULL, query2, buf.length - nused); > if (n > 0 > && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) > /* Use RESOLV_EDNS_BUFFER_SIZE because the receive > buffer can be reallocated. */ > - n = __res_nopt (ctx, n, query2, bufsize, > + n = __res_nopt (ctx, n, query2, buf.length, > RESOLV_EDNS_BUFFER_SIZE); > nquery2 = n; > } > @@ -169,7 +173,7 @@ __res_context_query (struct resolv_context *ctx, const char *name, > else > { > n = __res_context_mkquery (ctx, QUERY, name, class, type, NULL, > - query1, bufsize); > + query1, buf.length); > > if (n > 0 > && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) > @@ -181,27 +185,25 @@ __res_context_query (struct resolv_context *ctx, const char *name, > advertise = anslen; > else > advertise = RESOLV_EDNS_BUFFER_SIZE; > - n = __res_nopt (ctx, n, query1, bufsize, advertise); > + n = __res_nopt (ctx, n, query1, buf.length, advertise); > } > > nquery1 = n; > } > > - if (__glibc_unlikely (n <= 0) && !use_malloc) { > + if (__glibc_unlikely (n <= 0)) { > /* Retry just in case res_nmkquery failed because of too > short buffer. Shouldn't happen. */ > - bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * MAXPACKET; > - buf = malloc (bufsize); > - if (buf != NULL) { > - query1 = buf; > - use_malloc = 1; > + if (scratch_buffer_set_array_size (&buf, > + T_QUERY_A_AND_AAAA ? 2 : 1, > + MAXPACKET)) { > + query1 = buf.data; > goto again; > } > } > if (__glibc_unlikely (n <= 0)) { > RES_SET_H_ERRNO(statp, NO_RECOVERY); > - if (use_malloc) > - free (buf); > + scratch_buffer_free (&buf); > return (n); > } > > @@ -224,8 +226,7 @@ __res_context_query (struct resolv_context *ctx, const char *name, > answerp2_malloced); > } > > - if (use_malloc) > - free (buf); > + scratch_buffer_free (&buf); > if (n < 0) { > RES_SET_H_ERRNO(statp, TRY_AGAIN); > return (n); > -- > 2.34.1 >
On 14/09/23 17:37, Florian Weimer wrote: > * Adhemerval Zanella: > >> @@ -146,20 +150,20 @@ __res_context_query (struct resolv_context *ctx, const char *name, >> /* Align the buffer. */ >> int npad = ((nquery1 + __alignof__ (HEADER) - 1) >> & ~(__alignof__ (HEADER) - 1)) - nquery1; >> - if (n > bufsize - npad) >> + if (n > buf.length - npad) >> { >> n = -1; >> goto unspec_nomem; >> } >> int nused = n + npad; > > The alignment code shouldn't be necessary anymore. Indeed, I will update the patch.
diff --git a/resolv/res_query.c b/resolv/res_query.c index 049de91b95..b234db83c1 100644 --- a/resolv/res_query.c +++ b/resolv/res_query.c @@ -80,6 +80,7 @@ #include <stdlib.h> #include <string.h> #include <shlib-compat.h> +#include <scratch_buffer.h> #if PACKETSZ > 65536 #define MAXPACKET PACKETSZ @@ -114,11 +115,14 @@ __res_context_query (struct resolv_context *ctx, const char *name, struct __res_state *statp = ctx->resp; UHEADER *hp = (UHEADER *) answer; UHEADER *hp2; - int n, use_malloc = 0; - - size_t bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * QUERYSIZE; - u_char *buf = alloca (bufsize); - u_char *query1 = buf; + int n; + + /* It requires 2 times QUERYSIZE for type == T_QUERY_A_AND_AAAA. */ + struct scratch_buffer buf; + scratch_buffer_init (&buf); + _Static_assert (2 * QUERYSIZE <= sizeof (buf.__space.__c), + "scratch_buffer too small"); + u_char *query1 = buf.data; int nquery1 = -1; u_char *query2 = NULL; int nquery2 = 0; @@ -129,14 +133,14 @@ __res_context_query (struct resolv_context *ctx, const char *name, if (type == T_QUERY_A_AND_AAAA) { n = __res_context_mkquery (ctx, QUERY, name, class, T_A, NULL, - query1, bufsize); + query1, buf.length); if (n > 0) { if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) { /* Use RESOLV_EDNS_BUFFER_SIZE because the receive buffer can be reallocated. */ - n = __res_nopt (ctx, n, query1, bufsize, + n = __res_nopt (ctx, n, query1, buf.length, RESOLV_EDNS_BUFFER_SIZE); if (n < 0) goto unspec_nomem; @@ -146,20 +150,20 @@ __res_context_query (struct resolv_context *ctx, const char *name, /* Align the buffer. */ int npad = ((nquery1 + __alignof__ (HEADER) - 1) & ~(__alignof__ (HEADER) - 1)) - nquery1; - if (n > bufsize - npad) + if (n > buf.length - npad) { n = -1; goto unspec_nomem; } int nused = n + npad; - query2 = buf + nused; + query2 = buf.data + nused; n = __res_context_mkquery (ctx, QUERY, name, class, T_AAAA, - NULL, query2, bufsize - nused); + NULL, query2, buf.length - nused); if (n > 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) /* Use RESOLV_EDNS_BUFFER_SIZE because the receive buffer can be reallocated. */ - n = __res_nopt (ctx, n, query2, bufsize, + n = __res_nopt (ctx, n, query2, buf.length, RESOLV_EDNS_BUFFER_SIZE); nquery2 = n; } @@ -169,7 +173,7 @@ __res_context_query (struct resolv_context *ctx, const char *name, else { n = __res_context_mkquery (ctx, QUERY, name, class, type, NULL, - query1, bufsize); + query1, buf.length); if (n > 0 && (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0) @@ -181,27 +185,25 @@ __res_context_query (struct resolv_context *ctx, const char *name, advertise = anslen; else advertise = RESOLV_EDNS_BUFFER_SIZE; - n = __res_nopt (ctx, n, query1, bufsize, advertise); + n = __res_nopt (ctx, n, query1, buf.length, advertise); } nquery1 = n; } - if (__glibc_unlikely (n <= 0) && !use_malloc) { + if (__glibc_unlikely (n <= 0)) { /* Retry just in case res_nmkquery failed because of too short buffer. Shouldn't happen. */ - bufsize = (type == T_QUERY_A_AND_AAAA ? 2 : 1) * MAXPACKET; - buf = malloc (bufsize); - if (buf != NULL) { - query1 = buf; - use_malloc = 1; + if (scratch_buffer_set_array_size (&buf, + T_QUERY_A_AND_AAAA ? 2 : 1, + MAXPACKET)) { + query1 = buf.data; goto again; } } if (__glibc_unlikely (n <= 0)) { RES_SET_H_ERRNO(statp, NO_RECOVERY); - if (use_malloc) - free (buf); + scratch_buffer_free (&buf); return (n); } @@ -224,8 +226,7 @@ __res_context_query (struct resolv_context *ctx, const char *name, answerp2_malloced); } - if (use_malloc) - free (buf); + scratch_buffer_free (&buf); if (n < 0) { RES_SET_H_ERRNO(statp, TRY_AGAIN); return (n);