[PATCH 3.16.y-ckt 129/216] userns: Unbreak the unprivileged remount tests

Luis Henriques
2015-01-12T18:29:59Z

From: "Eric W. Biederman" <ebiederm@xmission.com>

commit db86da7cb76f797a1a8b445166a15cb922c6ff85 upstream.

A security fix in caused the way the unprivileged remount tests were
using user namespaces to break. Tweak the way user namespaces are
being used so the test works again.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
.../selftests/mount/unprivileged-remount-test.c | 32 ++++++++++++++++------
1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 9669d375625a..517785052f1c 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -53,17 +53,14 @@ static void die(char *fmt, ...)
exit(EXIT_FAILURE);
}

-static void write_file(char *filename, char *fmt, ...)
+static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
{
char buf[4096];
int fd;
ssize_t written;
int buf_len;
- va_list ap;

- va_start(ap, fmt);
buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
- va_end(ap);
if (buf_len < 0) {
die("vsnprintf failed: %s\n",
strerror(errno));
@@ -74,6 +71,8 @@ static void write_file(char *filename, char *fmt, ...)

fd = open(filename, O_WRONLY);
if (fd < 0) {
+ if ((errno == ENOENT) && enoent_ok)
+ return;
die("open of %s failed: %s\n",
filename, strerror(errno));
}
@@ -92,6 +91,26 @@ static void write_file(char *filename, char *fmt, ...)
}
}

+static void maybe_write_file(char *filename, char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vmaybe_write_file(true, filename, fmt, ap);
+ va_end(ap);
+
+}
+
+static void write_file(char *filename, char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ vmaybe_write_file(false, filename, fmt, ap);
+ va_end(ap);
+
+}
+
static int read_mnt_flags(const char *path)
{
int ret;
@@ -144,13 +163,10 @@ static void create_and_enter_userns(void)
strerror(errno));
}

+ maybe_write_file("/proc/self/setgroups", "deny");
write_file("/proc/self/uid_map", "0 %d 1", uid);
write_file("/proc/self/gid_map", "0 %d 1", gid);

- if (setgroups(0, NULL) != 0) {
- die("setgroups failed: %s\n",
- strerror(errno));
- }
if (setgid(0) != 0) {
die ("setgid(0) failed %s\n",
strerror(errno));
--
2.1.4