[lxc-devel] [lxd/master] nsexec: make cmdline parsing more reliable

[brauner on Github]

The following pull request was submitted through Github.
It can be accessed and reviewed at: https://github.com/lxc/lxd/pull/5497

This e-mail was sent by the LXC bot, direct replies will not reach the author
unless they happen to be subscribed to this list.

=== Description (from pull-request) ===
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>

From eab4f0aafdc812fe5fecc91bca0f910eb1555cae Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brau...@ubuntu.com>
Date: Sat, 16 Feb 2019 00:19:37 +0100
Subject: [PATCH] nsexec: make cmdline parsing more reliable

Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
---
 lxd/main_nsexec.go | 81 +++++++++++++++++++++++++++++++++++++---------
 1 file changed, 65 insertions(+), 16 deletions(-)

diff --git a/lxd/main_nsexec.go b/lxd/main_nsexec.go
index c03a5d24f0..770f87b90f 100644
--- a/lxd/main_nsexec.go
+++ b/lxd/main_nsexec.go
@@ -41,9 +41,16 @@ extern void forknet();
 extern void forkproxy();
 extern void forkuevent();
 
+// Make the compiler our memory housekeeper.
+static inline void __auto_free__(void *p)
+{
+       free(*(void **)p);
+}
+
+#define __do_free __attribute__((__cleanup__(__auto_free__)))
+
 // Command line parsing and tracking
-#define CMDLINE_SIZE (8 * PATH_MAX)
-char cmdline_buf[CMDLINE_SIZE];
+char *cmdline_buf = NULL;
 char *cmdline_cur = NULL;
 ssize_t cmdline_size = -1;
 
@@ -210,26 +217,68 @@ void attach_userns(int pid) {
        }
 }
 
-__attribute__((constructor)) void init(void) {
-       int cmdline;
+static ssize_t lxc_read_nointr(int fd, void *buf, size_t count)
+{
+       ssize_t ret;
+again:
+       ret = read(fd, buf, count);
+       if (ret < 0 && errno == EINTR)
+               goto again;
 
-       // Extract arguments
-       cmdline = open("/proc/self/cmdline", O_RDONLY);
-       if (cmdline < 0) {
-               error("error: open");
-               _exit(232);
+       return ret;
+}
+
+static char *file_to_buf(char *path, size_t *length)
+{
+       int fd;
+       char buf[PATH_MAX];
+       char *copy = NULL;
+
+       if (!length)
+               return NULL;
+
+       fd = open(path, O_RDONLY | O_CLOEXEC);
+       if (fd < 0)
+               return NULL;
+
+       *length = 0;
+       for (;;) {
+               int n;
+               char *old = copy;
+
+               n = lxc_read_nointr(fd, buf, sizeof(buf));
+               if (n < 0)
+                       goto on_error;
+               if (!n)
+                       break;
+
+               copy = realloc(old, (*length + n) * sizeof(*old));
+               if (!copy)
+                       goto on_error;
+
+               memcpy(copy + *length, buf, n);
+               *length += n;
        }
 
-       memset(cmdline_buf, 0, sizeof(cmdline_buf));
-       if ((cmdline_size = read(cmdline, cmdline_buf, sizeof(cmdline_buf)-1)) 
< 0) {
-               close(cmdline);
-               error("error: read");
+       close(fd);
+       return copy;
+
+on_error:
+       close(fd);
+       free(copy);
+
+       return NULL;
+}
+
+__attribute__((constructor)) void init(void) {
+       __do_free char *cmdline = NULL;
+
+       cmdline_buf = file_to_buf("/proc/self/cmdline", &cmdline_size);
+       if (!cmdline_buf)
                _exit(232);
-       }
-       close(cmdline);
 
        // Skip the first argument (but don't fail on missing second argument)
-       cmdline_cur = cmdline_buf;
+       cmdline = cmdline_cur = cmdline_buf;
        while (*cmdline_cur != 0)
                cmdline_cur++;
        cmdline_cur++;

_______________________________________________
lxc-devel mailing list
lxc-devel@lists.linuxcontainers.org
http://lists.linuxcontainers.org/listinfo/lxc-devel