overhaul system() and popen() to use vfork; fix various related bugs

[musl] / src / stdio / popen.c

diff --git a/src/stdio/popen.c b/src/stdio/popen.c
index 4f9d6e9..0c9f24e 100644 (file)
--- a/src/stdio/popen.c
+++ b/src/stdio/popen.c
@@ -1,18 +1,22 @@
+#include <fcntl.h>
 #include "stdio_impl.h"
+#include "pthread_impl.h"
 #include "syscall.h"
 
-static inline void nc_close(int fd)
+static void dummy_0()
 {
-       __syscall(SYS_close, fd);
 }
-#define close(x) nc_close(x)
+weak_alias(dummy_0, __acquire_ptc);
+weak_alias(dummy_0, __release_ptc);
+
+pid_t __vfork(void);
 
 FILE *popen(const char *cmd, const char *mode)
 {
-       int p[2];
-       int op;
+       int p[2], op, i;
        pid_t pid;
        FILE *f;
+       sigset_t old;
        const char *modes = "rw", *mi = strchr(modes, *mode);
 
        if (mi) {
@@ -22,29 +26,45 @@ FILE *popen(const char *cmd, const char *mode)
                return 0;
        }
        
-       if (pipe(p)) return NULL;
+       if (pipe2(p, O_CLOEXEC)) return NULL;
        f = fdopen(p[op], mode);
        if (!f) {
-               close(p[0]);
-               close(p[1]);
+               __syscall(SYS_close, p[0]);
+               __syscall(SYS_close, p[1]);
                return NULL;
        }
+
+       sigprocmask(SIG_BLOCK, SIGALL_SET, &old);
        
-       pid = fork();
-       switch (pid) {
-       case -1:
-               fclose(f);
-               close(p[0]);
-               close(p[1]);
-               return NULL;
-       case 0:
-               if (dup2(p[1-op], 1-op) < 0) _exit(127);
-               if (p[0] != 1-op) close(p[0]);
-               if (p[1] != 1-op) close(p[1]);
-               execl("/bin/sh", "sh", "-c", cmd, (char *)0);
-               _exit(127);
+       __acquire_ptc();
+       pid = __vfork();
+       __release_ptc();
+
+       if (pid) {
+               __syscall(SYS_close, p[1-op]);
+               sigprocmask(SIG_BLOCK, SIGALL_SET, &old);
+               if (pid < 0) {
+                       fclose(f);
+                       return 0;
+               }
+               f->pipe_pid = pid;
+               return f;
+       }
+
+       /* See notes in system.c for why this is needed. */
+       for (i=1; i<=8*__SYSCALL_SSLEN; i++) {
+               struct sigaction sa;
+               __libc_sigaction(i, 0, &sa);
+               if (sa.sa_handler!=SIG_IGN && sa.sa_handler!=SIG_DFL) {
+                       sa.sa_handler = SIG_DFL;
+                       __libc_sigaction(i, &sa, 0);
+               }
        }
-       close(p[1-op]);
-       f->pipe_pid = pid;
-       return f;
+       if (dup2(p[1-op], 1-op) < 0) _exit(127);
+       fcntl(1-op, F_SETFD, 0);
+       if (p[0] != 1-op) __syscall(SYS_close, p[0]);
+       if (p[1] != 1-op) __syscall(SYS_close, p[1]);
+       sigprocmask(SIG_SETMASK, &old, 0);
+       execl("/bin/sh", "sh", "-c", cmd, (char *)0);
+       _exit(127);
 }