attach, utils: bugfixes

- simply check /proc/self/ns
- improve SYSERROR() report
- use #define to prevent gcc & clang to use a VLA

Signed-off-by: Christian Brauner <christian.brauner@canonical.com>

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 9fe66a8e9962b21faaba7b6761dae1c53f2c2fdf..aac38ffe1fd9feba7d974747ebbaf9430f50691e 100644 (file)
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -220,7 +220,6 @@ static void lxc_proc_put_context_info(struct lxc_proc_context_info *ctx)
 
 static int lxc_attach_to_ns(pid_t pid, int which)
 {
-       char path[MAXPATHLEN];
        /* according to <http://article.gmane.org/gmane.linux.kernel.containers.lxc.devel/1429>,
         * the file for user namespaces in /proc/$pid/ns will be called
         * 'user' once the kernel supports it
@@ -235,8 +234,7 @@ static int lxc_attach_to_ns(pid_t pid, int which)
        int i, j, saved_errno;
 
 
-       snprintf(path, MAXPATHLEN, "/proc/%d/ns", pid);
-       if (access(path, X_OK)) {
+       if (access("/proc/self/ns", X_OK)) {
                ERROR("Does this kernel version support 'attach' ?");
                return -1;
        }
@@ -261,7 +259,7 @@ static int lxc_attach_to_ns(pid_t pid, int which)
                                close(fd[j]);
 
                        errno = saved_errno;
-                       SYSERROR("failed to open '%s'", path);
+                       SYSERROR("failed to open namespace: '%s'.", ns[i]);
                        return -1;
                }
        }

diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index 70f5aeb0d7ddff61a72f15b27c5ff592f625f011..9198340f69675a7597d9984d4515d2817f8e1ee6 100644 (file)
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -1972,17 +1972,18 @@ int lxc_append_string(char ***list, char *entry)
 int lxc_preserve_ns(const int pid, const char *ns)
 {
        int ret;
-       size_t len = 5 /* /proc */ + 21 /* /int_as_str */ + 3 /* /ns */ + 20 /* /NS_NAME */ + 1 /* \0 */;
-       char path[len];
+/* 5 /proc + 21 /int_as_str + 3 /ns + 20 /NS_NAME + 1 \0 */
+#define __NS_PATH_LEN 50
+       char path[__NS_PATH_LEN];
 
        /* This way we can use this function to also check whether namespaces
         * are supported by the kernel by passing in the NULL or the empty
         * string.
         */
-       ret = snprintf(path, len, "/proc/%d/ns%s%s", pid,
+       ret = snprintf(path, __NS_PATH_LEN, "/proc/%d/ns%s%s", pid,
                       !ns || strcmp(ns, "") == 0 ? "" : "/",
                       !ns || strcmp(ns, "") == 0 ? "" : ns);
-       if (ret < 0 || (size_t)ret >= len)
+       if (ret < 0 || (size_t)ret >= __NS_PATH_LEN)
                return -1;
 
        return open(path, O_RDONLY | O_CLOEXEC);