lxc-attach: Default to /bin/sh if shell cannot be determined or exec'd

If getpwuid() fails and also the fallback of spawning of a 'getent' process, and the user specified no command to execute, default to /bin/sh and only fail if even that is not available. This should ensure that unless the container is *really* weird, no matter what, the user should always end up with a shell when calling lxc-attach with no further arguments. Signed-off-by: Christian Seiler <christian@iwakd.de>

lxc-attach: Default to /bin/sh if shell cannot be determined or exec'd
21da9912 · Christian Seiler · Serge Hallyn · 905022f7 · 21da9912
Commit 21da9912 authored Mar 06, 2013 by Christian Seiler Committed by Serge Hallyn Mar 06, 2013
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lxc_attach.c src/lxc/lxc_attach.c +11 -5

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--- a/src/lxc/lxc_attach.c
+++ b/src/lxc/lxc_attach.c
@@ -452,15 +452,21 @@ int main(int argc, char *argv[])
                else
                        user_shell = passwd->pw_shell;

-		if (!user_shell) {
-			SYSERROR("failed to get passwd "		\
-				 "entry for uid '%d'", uid);
-			return -1;
+                if (user_shell) {
+			char *const args[] = {
+				user_shell,
+				NULL,
+			};
+
+			(void) execvp(args[0], args);
 		}

+		/* executed if either no passwd entry or execvp fails,
+		 * we will fall back on /bin/sh as a default shell
+		 */
 		{
 			char *const args[] = {
-				user_shell,
+				"/bin/sh",
 				NULL,
 			};