su: Segmentation Fault on unknown numerical uids

(cherry pick from commit 45948f910c69d354cc3f7e81631445d83ebadc3d)

e.g.

su 2999,2999,2999 echo hello
Segmentation Fault

return from getpwuid is NULL. KISS we opt to unset LOGNAME and USER

Change-Id: I7e7eddacfd6857f83482727eb5ec5c51b9170039

1 files changed, 7 insertions, 2 deletions

diff --git a/su/su.c b/su/su.c
index d932c1ba..ea61f93d 100644
--- a/su/su.c
+++ b/su/su.c
@@ -122,8 +122,13 @@ int main(int argc, char** argv) {
     setenv("PATH", _PATH_DEFPATH, 1);
     unsetenv("IFS");
     struct passwd* pw = getpwuid(uid);
-    setenv("LOGNAME", pw->pw_name, 1);
-    setenv("USER", pw->pw_name, 1);
+    if (pw) {
+        setenv("LOGNAME", pw->pw_name, 1);
+        setenv("USER", pw->pw_name, 1);
+    } else {
+        unsetenv("LOGNAME");
+        unsetenv("USER");
+    }
 
     // Set up the arguments for exec.
     char* exec_args[argc + 1];  // Having too much space is fine.