6 files changed, 55 insertions, 33 deletions
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 048323b137..36f50ae7a2 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -2692,14 +2692,7 @@ static FILE *fopen_noinh_readbin(char *filename)
     return NULL;
   }
 
-#ifdef HAVE_FD_CLOEXEC
-  {
-    int fdflags = fcntl(fd_tmp, F_GETFD);
-    if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0) {
-      (void)fcntl(fd_tmp, F_SETFD, fdflags | FD_CLOEXEC);
-    }
-  }
-#endif
+  (void)os_set_cloexec(fd_tmp);
 
   return fdopen(fd_tmp, READBIN);
 }
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 040df707de..9c64be6d0c 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -1742,16 +1742,11 @@ failed:
   }
 # endif
 
-  if (!read_buffer && !read_stdin)
-    close(fd);                                  /* errors are ignored */
-#ifdef HAVE_FD_CLOEXEC
-  else {
-    int fdflags = fcntl(fd, F_GETFD);
-    if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0) {
-      (void)fcntl(fd, F_SETFD, fdflags | FD_CLOEXEC);
-    }
+  if (!read_buffer && !read_stdin) {
+    close(fd);  // errors are ignored
+  } else {
+    (void)os_set_cloexec(fd);
   }
-#endif
   xfree(buffer);
 
   if (read_stdin) {
diff --git a/src/nvim/memfile.c b/src/nvim/memfile.c
index 43412e3916..5d6639c4d0 100644
--- a/src/nvim/memfile.c
+++ b/src/nvim/memfile.c
@@ -909,12 +909,7 @@ static bool mf_do_open(memfile_T *mfp, char_u *fname, int flags)
     return false;
   }
 
-#ifdef HAVE_FD_CLOEXEC
-  int fdflags = fcntl(mfp->mf_fd, F_GETFD);
-  if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0) {
-    (void)fcntl(mfp->mf_fd, F_SETFD, fdflags | FD_CLOEXEC);
-  }
-#endif
+  (void)os_set_cloexec(mfp->mf_fd);
 #ifdef HAVE_SELINUX
   mch_copy_sec(fname, mfp->mf_fname);
 #endif
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 1a315fce8b..f9d3751390 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -439,14 +439,7 @@ void ml_setname(buf_T *buf)
       EMSG(_("E301: Oops, lost the swap file!!!"));
       return;
     }
-#ifdef HAVE_FD_CLOEXEC
-    {
-      int fdflags = fcntl(mfp->mf_fd, F_GETFD);
-      if (fdflags >= 0 && (fdflags & FD_CLOEXEC) == 0) {
-        (void)fcntl(mfp->mf_fd, F_SETFD, fdflags | FD_CLOEXEC);
-      }
-    }
-#endif
+    (void)os_set_cloexec(mfp->mf_fd);
   }
   if (!success)
     EMSG(_("E302: Could not rename swap file"));
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index e930561234..af60e1b7af 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -391,6 +391,35 @@ int os_open(const char* path, int flags, int mode)
   return r;
 }
 
+/// Sets file descriptor `fd` to close-on-exec.
+//
+// @return -1 if failed to set, 0 otherwise.
+int os_set_cloexec(const int fd)
+{
+#ifdef HAVE_FD_CLOEXEC
+  int e;
+  int fdflags = fcntl(fd, F_GETFD);
+  if (fdflags < 0) {
+    e = errno;
+    ELOG("Failed to get flags on descriptor %d: %s", fd, strerror(e));
+    errno = e;
+    return -1;
+  }
+  if ((fdflags & FD_CLOEXEC) == 0
+      && fcntl(fd, F_SETFD, fdflags | FD_CLOEXEC) < 0) {
+    e = errno;
+    ELOG("Failed to set CLOEXEC on descriptor %d: %s", fd, strerror(e));
+    errno = e;
+    return -1;
+  }
+  return 0;
+#endif
+
+  // No FD_CLOEXEC flag. On Windows, the file should have been opened with
+  // O_NOINHERIT anyway.
+  return -1;
+}
+
 /// Close a file
 ///
 /// @return 0 or libuv error code on failure.
diff --git a/src/nvim/os/pty_process_unix.c b/src/nvim/os/pty_process_unix.c
index f5ba0c2612..71a5e13de5 100644
--- a/src/nvim/os/pty_process_unix.c
+++ b/src/nvim/os/pty_process_unix.c
@@ -73,6 +73,13 @@ int pty_process_spawn(PtyProcess *ptyproc)
     goto error;
   }
 
+  // Other jobs and providers should not get a copy of this file descriptor.
+  if (os_set_cloexec(master) == -1) {
+    status = -errno;
+    ELOG("Failed to set CLOEXEC on ptmx file descriptor");
+    goto error;
+  }
+
   if (proc->in
       && (status = set_duplicating_descriptor(master, &proc->in->uv.pipe))) {
     goto error;
@@ -215,14 +222,24 @@ static int set_duplicating_descriptor(int fd, uv_pipe_t *pipe)
     ELOG("Failed to dup descriptor %d: %s", fd, strerror(errno));
     return status;
   }
+
+  if (os_set_cloexec(fd_dup) == -1) {
+    status = -errno;
+    ELOG("Failed to set CLOEXEC on duplicate fd");
+    goto error;
+  }
+
   status = uv_pipe_open(pipe, fd_dup);
   if (status) {
     ELOG("Failed to set pipe to descriptor %d: %s",
          fd_dup, uv_strerror(status));
-    close(fd_dup);
-    return status;
+    goto error;
   }
   return status;
+
+error:
+  close(fd_dup);
+  return status;
 }
 
 static void chld_handler(uv_signal_t *handle, int signum)