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Merge pull request #22923 from poettering/userns-check-refactor

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virt: minor running_in_userns() modernizations
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Luca Boccassi 2022-03-31 22:11:03 +01:00 committed by GitHub
commit 58270534bf
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1 changed files with 18 additions and 23 deletions
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41
src/basic/virt.c
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@ -12,6 +12,7 @@
#include "cgroup-util.h"
#include "dirent-util.h"
#include "env-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "macro.h"
@ -791,10 +792,7 @@ int detect_virtualization(void) {
static int userns_has_mapping(const char *name) {
_cleanup_fclose_ FILE *f = NULL;
_cleanup_free_ char *buf = NULL;
size_t n_allocated = 0;
ssize_t n;
uint32_t a, b, c;
uid_t a, b, c;
int r;
f = fopen(name, "re");
@ -803,19 +801,17 @@ static int userns_has_mapping(const char *name) {
return errno == ENOENT ? false : -errno;
}
n = getline(&buf, &n_allocated, f);
if (n < 0) {
if (feof(f)) {
log_debug("%s is empty, we're in an uninitialized user namespace", name);
return true;
}
errno = 0;
r = fscanf(f, UID_FMT " " UID_FMT " " UID_FMT "\n", &a, &b, &c);
if (r == EOF) {
if (ferror(f))
return log_debug_errno(errno_or_else(EIO), "Failed to read %s: %m", name);
return log_debug_errno(errno, "Failed to read %s: %m", name);
log_debug("%s is empty, we're in an uninitialized user namespace", name);
return true;
}
r = sscanf(buf, "%"PRIu32" %"PRIu32" %"PRIu32, &a, &b, &c);
if (r < 3)
return log_debug_errno(errno, "Failed to parse %s: %m", name);
if (r != 3)
return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG), "Failed to parse %s: %m", name);
if (a == 0 && b == 0 && c == UINT32_MAX) {
/* The kernel calls mappings_overlap() and does not allow overlaps */
@ -840,19 +836,18 @@ int running_in_userns(void) {
if (r != 0)
return r;
/* "setgroups" file was added in kernel v3.18-rc6-15-g9cc46516dd. It is also
* possible to compile a kernel without CONFIG_USER_NS, in which case "setgroups"
* also does not exist. We cannot distinguish those two cases, so assume that
* we're running on a stripped-down recent kernel, rather than on an old one,
* and if the file is not found, return false.
*/
r = read_one_line_file("/proc/self/setgroups", &line);
/* "setgroups" file was added in kernel v3.18-rc6-15-g9cc46516dd. It is also possible to compile a
* kernel without CONFIG_USER_NS, in which case "setgroups" also does not exist. We cannot
* distinguish those two cases, so assume that we're running on a stripped-down recent kernel, rather
* than on an old one, and if the file is not found, return false. */
r = read_virtual_file("/proc/self/setgroups", SIZE_MAX, &line, NULL);
if (r < 0) {
log_debug_errno(r, "/proc/self/setgroups: %m");
return r == -ENOENT ? false : r;
}
truncate_nl(line);
strstrip(line); /* remove trailing newline */
r = streq(line, "deny");
/* See user_namespaces(7) for a description of this "setgroups" contents. */
log_debug("/proc/self/setgroups contains \"%s\", %s user namespace", line, r ? "in" : "not in");