From bfdbb7089ab9bdc458340ac8353ee181393a2609 Mon Sep 17 00:00:00 2001
From: Bob Lantz <rlantz@cs.stanford.edu>
Date: Tue, 26 Aug 2014 14:08:28 -0700
Subject: [PATCH] Fall back to chroot() if setns() fails for mnt namespace
fixes #347
---
mnexec.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/mnexec.c b/mnexec.c
index c7103d46..7f17494d 100644
--- a/mnexec.c
+++ b/mnexec.c
@@ -140,9 +140,9 @@ int main(int argc, char *argv[])
fflush(stdout);
break;
case 'a':
- /* Attach to pid's network namespace and mount namespace*/
+ /* Attach to pid's network namespace and mount namespace */
pid = atoi(optarg);
- sprintf(path, "/proc/%d/ns/net", pid );
+ sprintf(path, "/proc/%d/ns/net", pid);
nsid = open(path, O_RDONLY);
if (nsid < 0) {
perror(path);
@@ -152,15 +152,16 @@ int main(int argc, char *argv[])
perror("setns");
return 1;
}
- sprintf(path, "/proc/%d/ns/mnt", pid );
+ /* Plan A: call setns() to attach to mount namespace */
+ sprintf(path, "/proc/%d/ns/mnt", pid);
nsid = open(path, O_RDONLY);
- if (nsid < 0) {
- perror(path);
- return 1;
- }
- if (setns(nsid, 0) != 0) {
- perror("setns");
- return 1;
+ if (nsid < 0 || setns(nsid, 0) != 0) {
+ /* Plan B: chroot into pid's root file system */
+ sprintf(path, "/proc/%d/root", pid);
+ if (chroot(path) < 0) {
+ perror(path);
+ return 1;
+ }
}
break;
case 'g':
--
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