check for fd exhaustion in forkpty

[musl] / src / misc / forkpty.c

diff --git a/src/misc/forkpty.c b/src/misc/forkpty.c
index 0bbf2de..07f8d01 100644 (file)
--- a/src/misc/forkpty.c
+++ b/src/misc/forkpty.c
@@ -1,14 +1,25 @@
 #include <pty.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
+#include <fcntl.h>
 
 int forkpty(int *m, char *name, const struct termios *tio, const struct winsize *ws)
 {
-       int s;
+       int s, t, i, istmp[3]={0};
        pid_t pid;
 
        if (openpty(m, &s, name, tio, ws) < 0) return -1;
-       pid = fork();
+
+       /* Ensure before forking that we don't exceed fd limit */
+       for (i=0; i<3; i++) {
+               if (fcntl(i, F_GETFL) < 0) {
+                       t = fcntl(s, F_DUPFD, i);
+                       if (t<0) break;
+                       else if (t!=i) close(t);
+                       else istmp[i] = 1;
+               }
+       }
+       pid = i==3 ? fork() : -1;
        if (!pid) {
                close(*m);
                setsid();
@@ -19,6 +30,8 @@ int forkpty(int *m, char *name, const struct termios *tio, const struct winsize
                if (s>2) close(s);
                return 0;
        }
+       for (i=0; i<3; i++)
+               if (istmp[i]) close(i);
        close(s);
        if (pid < 0) close(*m);
        return pid;