Commit 947a3a1be9

Andrew Kelley <andrew@ziglang.org>
2024-05-28 00:55:32
std.process.Child: fix spawning child proc with new cwd fd
Before this fix, the dup2 of the progress pipe was clobbering the cwd fd, causing the fchdir to return ENOTDIR in between fork() and exec().
master
1 parent b7889f2
Changed files (1)
lib
std
process
Child.zig
lib/std/process/Child.zig
@@ -654,7 +654,6 @@ fn spawnPosix(self: *ChildProcess) SpawnError!void {
         setUpChildIo(self.stdin_behavior, stdin_pipe[0], posix.STDIN_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
         setUpChildIo(self.stdout_behavior, stdout_pipe[1], posix.STDOUT_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
         setUpChildIo(self.stderr_behavior, stderr_pipe[1], posix.STDERR_FILENO, dev_null_fd) catch |err| forkChildErrReport(err_pipe[1], err);
-        if (prog_pipe[1] != -1) posix.dup2(prog_pipe[1], prog_fileno) catch |err| forkChildErrReport(err_pipe[1], err);
 
         if (self.cwd_dir) |cwd| {
             posix.fchdir(cwd.fd) catch |err| forkChildErrReport(err_pipe[1], err);
@@ -662,6 +661,10 @@ fn spawnPosix(self: *ChildProcess) SpawnError!void {
             posix.chdir(cwd) catch |err| forkChildErrReport(err_pipe[1], err);
         }
 
+        // Must happen after fchdir above, the cwd file descriptor might be
+        // equal to prog_fileno and be clobbered by this dup2 call.
+        if (prog_pipe[1] != -1) posix.dup2(prog_pipe[1], prog_fileno) catch |err| forkChildErrReport(err_pipe[1], err);
+
         if (self.gid) |gid| {
             posix.setregid(gid, gid) catch |err| forkChildErrReport(err_pipe[1], err);
         }