Fix a couple of bugs: check mode is legal; open file and check success before

calling vfork.

diff --git a/libc/stdio/popen.c b/libc/stdio/popen.c
index 7a00e57..bc91bb7 100644 (file)
--- a/libc/stdio/popen.c
+++ b/libc/stdio/popen.c
@@ -1,46 +1,66 @@
+/*
+ * Modified     3/03/2001       Manuel Novoa III
+ *
+ * Added check for legal mode arg.
+ * Call fdopen and check return value before forking.
+ * Reduced code size by using variables pr and pnr instead of array refs.
+ */
+
 #include <stdio.h>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <errno.h>
 
-
-FILE *popen (const char *command, const char *modes)
+FILE *popen (const char *command, const char *mode)
 {
+       FILE *fp;
        int pipe_fd[2];
        int pid, reading;
+       int pr, pnr;
 
-       if (pipe(pipe_fd) < 0)
-               return NULL;
-       reading = (modes[0] == 'r');
-
-       pid = vfork();
-       if (pid < 0) {
-               close(pipe_fd[0]);
-               close(pipe_fd[1]);
-               return NULL;
-       }
-       if (pid == 0) {
-               close(pipe_fd[!reading]);
-               close(reading);
-               if (pipe_fd[reading] != reading) {
-                       dup2(pipe_fd[reading], reading);
-                       close(pipe_fd[reading]);
+       reading = (mode[0] == 'r');
+       if ((!reading && (mode[0] != 'w')) || mode[1]) {
+               errno = EINVAL;                 /* Invalid mode arg. */
+       } else if (pipe(pipe_fd) == 0) {
+               pr = pipe_fd[reading];
+               pnr = pipe_fd[1-reading];
+               if ((fp = fdopen(pnr, mode)) != NULL) {
+                       if ((pid = vfork()) == 0) {     /* vfork -- child */
+                               close(pnr);
+                               close(reading);
+                               if (pr != reading) {
+                                       dup2(pr, reading);
+                                       close(pr);
+                               }
+                               execl("/bin/sh", "sh", "-c", command, (char *) 0);
+                               _exit(255);             /* execl failed! */
+                       } else {                        /* vfork -- parent or failed */
+                               close(pr);
+                               if (pid > 0) {  /* vfork -- parent */
+                                       return fp;
+                               } else {                /* vfork -- failed! */
+                                       fclose(fp);
+                               }
+                       }
+               } else {                                /* fdopen failed */
+                       close(pr);
+                       close(pnr);
                }
-
-               execl("/bin/sh", "sh", "-c", command, (char *) 0);
-               _exit(255);
        }
-
-       close(pipe_fd[reading]);
-       return fdopen(pipe_fd[!reading], modes);
+       return NULL;
 }
 
 int pclose(FILE *fd)
 {
        int waitstat;
 
-       if (fclose(fd) != 0)
+       if (fclose(fd) != 0) {
                return EOF;
+       }
        wait(&waitstat);
        return waitstat;
 }
+
+
+