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