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systemd/SOURCES/0055-nspawn-beef-up-netns-c...

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From 2115fcc1e673079fe76e949ac0904267075c25a4 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 31 Oct 2018 13:04:20 +0100
Subject: [PATCH] nspawn: beef up netns checking a bit, for compat with old
kernels
Fixes: #10544
Cherry-picked from: 6619ad889da260cf83079cc74a85d571acd1df5a
---
src/basic/stat-util.c | 40 +++++++++++++++++++++++++++++++++++----
src/nspawn/nspawn.c | 8 +++++---
src/test/test-stat-util.c | 15 +++++++++++++++
3 files changed, 56 insertions(+), 7 deletions(-)
diff --git a/src/basic/stat-util.c b/src/basic/stat-util.c
index 07154e25bb..26aee9bad6 100644
--- a/src/basic/stat-util.c
+++ b/src/basic/stat-util.c
@@ -204,15 +204,47 @@ int fd_is_network_fs(int fd) {
}
int fd_is_network_ns(int fd) {
+ struct statfs s;
int r;
- r = fd_is_fs_type(fd, NSFS_MAGIC);
- if (r <= 0)
- return r;
+ /* Checks whether the specified file descriptor refers to a network namespace. On old kernels there's no nice
+ * way to detect that, hence on those we'll return a recognizable error (EUCLEAN), so that callers can handle
+ * this somewhat nicely.
+ *
+ * This function returns > 0 if the fd definitely refers to a network namespace, 0 if it definitely does not
+ * refer to a network namespace, -EUCLEAN if we can't determine, and other negative error codes on error. */
+
+ if (fstatfs(fd, &s) < 0)
+ return -errno;
+
+ if (!is_fs_type(&s, NSFS_MAGIC)) {
+ /* On really old kernels, there was no "nsfs", and network namespace sockets belonged to procfs
+ * instead. Handle that in a somewhat smart way. */
+
+ if (is_fs_type(&s, PROC_SUPER_MAGIC)) {
+ struct statfs t;
+
+ /* OK, so it is procfs. Let's see if our own network namespace is procfs, too. If so, then the
+ * passed fd might refer to a network namespace, but we can't know for sure. In that case,
+ * return a recognizable error. */
+
+ if (statfs("/proc/self/ns/net", &t) < 0)
+ return -errno;
+
+ if (s.f_type == t.f_type)
+ return -EUCLEAN; /* It's possible, we simply don't know */
+ }
+
+ return 0; /* No! */
+ }
r = ioctl(fd, NS_GET_NSTYPE);
- if (r < 0)
+ if (r < 0) {
+ if (errno == ENOTTY) /* Old kernels didn't know this ioctl, let's also return a recognizable error in that case */
+ return -EUCLEAN;
+
return -errno;
+ }
return r == CLONE_NEWNET;
}
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 56877bd932..8aec893a69 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -3701,10 +3701,12 @@ static int run(int master,
return log_error_errno(errno, "Cannot open file %s: %m", arg_network_namespace_path);
r = fd_is_network_ns(netns_fd);
- if (r < 0 && r != -ENOTTY)
+ if (r == -EUCLEAN)
+ log_debug_errno(r, "Cannot determine if passed network namespace path '%s' really refers to a network namespace, assuming it does.", arg_network_namespace_path);
+ else if (r < 0)
return log_error_errno(r, "Failed to check %s fs type: %m", arg_network_namespace_path);
- if (r == 0) {
- log_error("Path %s doesn't refer to a network namespace", arg_network_namespace_path);
+ else if (r == 0) {
+ log_error("Path %s doesn't refer to a network namespace, refusing.", arg_network_namespace_path);
return -EINVAL;
}
}
diff --git a/src/test/test-stat-util.c b/src/test/test-stat-util.c
index 43f56a6c20..2b0564d8a0 100644
--- a/src/test/test-stat-util.c
+++ b/src/test/test-stat-util.c
@@ -67,11 +67,26 @@ static void test_path_is_temporary_fs(void) {
assert_se(path_is_temporary_fs("/i-dont-exist") == -ENOENT);
}
+static void test_fd_is_network_ns(void) {
+ _cleanup_close_ int fd = -1;
+ assert_se(fd_is_network_ns(STDIN_FILENO) == 0);
+ assert_se(fd_is_network_ns(STDERR_FILENO) == 0);
+ assert_se(fd_is_network_ns(STDOUT_FILENO) == 0);
+
+ assert_se((fd = open("/proc/self/ns/mnt", O_CLOEXEC|O_RDONLY)) >= 0);
+ assert_se(IN_SET(fd_is_network_ns(fd), 0, -EUCLEAN));
+ fd = safe_close(fd);
+
+ assert_se((fd = open("/proc/self/ns/net", O_CLOEXEC|O_RDONLY)) >= 0);
+ assert_se(IN_SET(fd_is_network_ns(fd), 1, -EUCLEAN));
+}
+
int main(int argc, char *argv[]) {
test_files_same();
test_is_symlink();
test_path_is_fs_type();
test_path_is_temporary_fs();
+ test_fd_is_network_ns();
return 0;
}