48 lines
1.1 KiB
C
48 lines
1.1 KiB
C
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/*
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* Utility routines.
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*
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* Copyright (C) 2017 Denys Vlasenko
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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//kbuild:lib-y += bb_getgroups.o
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#include "libbb.h"
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gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
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{
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int n = ngroups ? *ngroups : 0;
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/* getgroups may be a bit expensive, try to use it only once */
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if (n < 32)
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n = 32;
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for (;;) {
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// FIXME: ash tries so hard to not die on OOM (when we are called from test),
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// and we spoil it with just one xrealloc here
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group_array = xrealloc(group_array, (n+1) * sizeof(group_array[0]));
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n = getgroups(n, group_array);
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/*
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* If buffer is too small, kernel does not return new_n > n.
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* It returns -1 and EINVAL:
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*/
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if (n >= 0) {
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/* Terminator for bb_getgroups(NULL, NULL) usage */
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group_array[n] = (gid_t) -1;
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break;
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}
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if (errno == EINVAL) { /* too small? */
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/* This is the way to ask kernel how big the array is */
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n = getgroups(0, group_array);
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continue;
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}
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/* Some other error (should never happen on Linux) */
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bb_perror_msg_and_die("getgroups");
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}
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if (ngroups)
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*ngroups = n;
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return group_array;
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}
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