1ecca8439d
if the euid!=owner of the userns, the kernel returns EPERM when trying to write the uidmap and there is no CAP_SYS_ADMIN in the parent namespace. Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
208 lines
6.6 KiB
C
208 lines
6.6 KiB
C
/*
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* Copyright (c) 2013 Eric Biederman
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the copyright holders or contributors may not be used to
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* endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <config.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include "prototypes.h"
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#include "idmapping.h"
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#include <sys/prctl.h>
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#if HAVE_SYS_CAPABILITY_H
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# include <sys/capability.h>
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#endif
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struct map_range *get_map_ranges(int ranges, int argc, char **argv)
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{
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struct map_range *mappings, *mapping;
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int idx, argidx;
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if (ranges < 0 || argc < 0) {
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fprintf(stderr, "%s: error calculating number of arguments\n", Prog);
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return NULL;
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}
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if (ranges != ((argc + 2) / 3)) {
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fprintf(stderr, "%s: ranges: %u is wrong for argc: %d\n", Prog, ranges, argc);
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return NULL;
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}
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if ((ranges * 3) > argc) {
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fprintf(stderr, "ranges: %u argc: %d\n",
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ranges, argc);
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fprintf(stderr,
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_( "%s: Not enough arguments to form %u mappings\n"),
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Prog, ranges);
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return NULL;
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}
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mappings = calloc(ranges, sizeof(*mappings));
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if (!mappings) {
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fprintf(stderr, _( "%s: Memory allocation failure\n"),
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Prog);
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exit(EXIT_FAILURE);
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}
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/* Gather up the ranges from the command line */
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mapping = mappings;
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for (idx = 0, argidx = 0; idx < ranges; idx++, argidx += 3, mapping++) {
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if (!getulong(argv[argidx + 0], &mapping->upper)) {
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free(mappings);
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return NULL;
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}
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if (!getulong(argv[argidx + 1], &mapping->lower)) {
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free(mappings);
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return NULL;
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}
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if (!getulong(argv[argidx + 2], &mapping->count)) {
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free(mappings);
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return NULL;
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}
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if (ULONG_MAX - mapping->upper <= mapping->count || ULONG_MAX - mapping->lower <= mapping->count) {
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fprintf(stderr, _( "%s: subuid overflow detected.\n"), Prog);
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exit(EXIT_FAILURE);
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}
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if (mapping->upper > UINT_MAX ||
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mapping->lower > UINT_MAX ||
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mapping->count > UINT_MAX) {
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fprintf(stderr, _( "%s: subuid overflow detected.\n"), Prog);
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exit(EXIT_FAILURE);
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}
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if (mapping->lower + mapping->count > UINT_MAX ||
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mapping->upper + mapping->count > UINT_MAX) {
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fprintf(stderr, _( "%s: subuid overflow detected.\n"), Prog);
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exit(EXIT_FAILURE);
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}
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if (mapping->lower + mapping->count < mapping->lower ||
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mapping->upper + mapping->count < mapping->upper) {
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/* this one really shouldn't be possible given previous checks */
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fprintf(stderr, _( "%s: subuid overflow detected.\n"), Prog);
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exit(EXIT_FAILURE);
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}
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}
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return mappings;
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}
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/* Number of ascii digits needed to print any unsigned long in decimal.
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* There are approximately 10 bits for every 3 decimal digits.
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* So from bits to digits the formula is roundup((Number of bits)/10) * 3.
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* For common sizes of integers this works out to:
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* 2bytes --> 6 ascii estimate -> 65536 (5 real)
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* 4bytes --> 12 ascii estimated -> 4294967296 (10 real)
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* 8bytes --> 21 ascii estimated -> 18446744073709551616 (20 real)
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* 16bytes --> 39 ascii estimated -> 340282366920938463463374607431768211456 (39 real)
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*/
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#define ULONG_DIGITS ((((sizeof(unsigned long) * CHAR_BIT) + 9)/10)*3)
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void write_mapping(int proc_dir_fd, int ranges, struct map_range *mappings,
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const char *map_file, uid_t uid)
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{
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int idx;
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struct map_range *mapping;
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size_t bufsize;
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char *buf, *pos;
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int fd;
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#if HAVE_SYS_CAPABILITY_H
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struct __user_cap_header_struct hdr = { _LINUX_CAPABILITY_VERSION_3, 0 };
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struct __user_cap_data_struct data[2] = { { 0 } };
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#endif
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bufsize = ranges * ((ULONG_DIGITS + 1) * 3);
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pos = buf = xmalloc(bufsize);
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#if HAVE_SYS_CAPABILITY_H
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if (capget(&hdr, data) < 0) {
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fprintf(stderr, _("%s: Could not get capabilities\n"), Prog);
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exit(EXIT_FAILURE);
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}
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if (!(data[0].effective & CAP_TO_MASK(CAP_SYS_ADMIN)) &&
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uid != geteuid()) {
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bool uid_map;
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if (strcmp(map_file, "uid_map") == 0) {
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uid_map = true;
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} else if (strcmp(map_file, "gid_map") == 0) {
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uid_map = false;
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} else {
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fprintf(stderr, _("%s: Invalid map file %s specified\n"), Prog, map_file);
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exit(EXIT_FAILURE);
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}
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if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0) {
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fprintf(stderr, _("%s: Could not prctl(PR_SET_KEEPCAPS)\n"), Prog);
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exit(EXIT_FAILURE);
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}
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if (seteuid(uid) < 0) {
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fprintf(stderr, _("%s: Could not seteuid to %d\n"), Prog, uid);
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exit(EXIT_FAILURE);
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}
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memset(data, 0, sizeof(data));
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data[0].effective = data[0].permitted = CAP_TO_MASK(uid_map ? CAP_SETUID : CAP_SETGID);
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if (capset(&hdr, data) < 0) {
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fprintf(stderr, _("%s: Could not set caps\n"), Prog);
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exit(EXIT_FAILURE);
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}
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}
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#endif
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/* Build the mapping command */
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mapping = mappings;
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for (idx = 0; idx < ranges; idx++, mapping++) {
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/* Append this range to the string that will be written */
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int written = snprintf(pos, bufsize - (pos - buf),
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"%lu %lu %lu\n",
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mapping->upper,
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mapping->lower,
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mapping->count);
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if ((written <= 0) || (written >= (bufsize - (pos - buf)))) {
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fprintf(stderr, _("%s: snprintf failed!\n"), Prog);
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exit(EXIT_FAILURE);
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}
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pos += written;
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}
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/* Write the mapping to the mapping file */
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fd = openat(proc_dir_fd, map_file, O_WRONLY);
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if (fd < 0) {
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fprintf(stderr, _("%s: open of %s failed: %s\n"),
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Prog, map_file, strerror(errno));
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exit(EXIT_FAILURE);
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}
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if (write(fd, buf, pos - buf) != (pos - buf)) {
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fprintf(stderr, _("%s: write to %s failed: %s\n"),
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Prog, map_file, strerror(errno));
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exit(EXIT_FAILURE);
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}
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close(fd);
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}
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