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setsourcefilter: Replace alloca with a scratch_buffer.
Use a scratch_buffer rather than either alloca or malloc to reduce the possibility of a stack overflow. Suggested-by: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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@ -16,13 +16,10 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <alloca.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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#include <scratch_buffer.h>
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#include "getsourcefilter.h"
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@ -34,17 +31,12 @@ setsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
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/* We have to create an struct ip_msfilter object which we can pass
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to the kernel. */
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size_t needed = GROUP_FILTER_SIZE (numsrc);
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int use_alloca = __libc_use_alloca (needed);
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struct group_filter *gf;
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if (use_alloca)
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gf = (struct group_filter *) alloca (needed);
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else
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{
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gf = (struct group_filter *) malloc (needed);
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if (gf == NULL)
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return -1;
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}
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struct scratch_buffer buf;
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scratch_buffer_init (&buf);
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if (!scratch_buffer_set_array_size (&buf, 1, needed))
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return -1;
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struct group_filter *gf = buf.data;
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gf->gf_interface = interface;
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memcpy (&gf->gf_group, group, grouplen);
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@ -63,12 +55,7 @@ setsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
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else
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result = __setsockopt (s, sol, MCAST_MSFILTER, gf, needed);
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if (! use_alloca)
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{
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int save_errno = errno;
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free (gf);
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__set_errno (save_errno);
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}
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scratch_buffer_free (&buf);
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return result;
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}
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