jobstart(): Fix hang on non-executable cwd #9204

* os/fs.c: add os_isdir_executable()
* eval.c: fix hang on job start caused by non-executable cwd option
* channel.c: assert cwd is an executable directory
* test: jobstart() produces error when using non-executable cwd

4 files changed, 36 insertions, 3 deletions

diff --git a/src/nvim/channel.c b/src/nvim/channel.c
index 259f1cc600..58a34acb22 100644
--- a/src/nvim/channel.c
+++ b/src/nvim/channel.c
@@ -284,6 +284,8 @@ Channel *channel_job_start(char **argv, CallbackReader on_stdout,
                            uint16_t pty_width, uint16_t pty_height,
                            char *term_name, varnumber_T *status_out)
 {
+  assert(cwd == NULL || os_isdir_executable(cwd));
+
   Channel *chan = channel_alloc(kChannelStreamProc);
   chan->on_stdout = on_stdout;
   chan->on_stderr = on_stderr;
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 2fb9bd7367..9c7af0a87d 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -11724,7 +11724,7 @@ static void f_jobstart(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     if (new_cwd && strlen(new_cwd) > 0) {
       cwd = new_cwd;
       // The new cwd must be a directory.
-      if (!os_isdir((char_u *)cwd)) {
+      if (!os_isdir_executable((const char *)cwd)) {
         EMSG2(_(e_invarg2), "expected valid directory");
         shell_free_argv(argv);
         return;
@@ -16769,7 +16769,7 @@ static void f_termopen(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     if (new_cwd && *new_cwd != NUL) {
       cwd = new_cwd;
       // The new cwd must be a directory.
-      if (!os_isdir((const char_u *)cwd)) {
+      if (!os_isdir_executable((const char *)cwd)) {
         EMSG2(_(e_invarg2), "expected valid directory");
         shell_free_argv(argv);
         return;
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index cf00fd4f82..9a4391a0ae 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -110,7 +110,7 @@ bool os_isrealdir(const char *name)
 
 /// Check if the given path is a directory or not.
 ///
-/// @return `true` if `fname` is a directory.
+/// @return `true` if `name` is a directory.
 bool os_isdir(const char_u *name)
   FUNC_ATTR_NONNULL_ALL
 {
@@ -126,6 +126,25 @@ bool os_isdir(const char_u *name)
   return true;
 }
 
+/// Check if the given path is a directory and is executable.
+/// Gives the same results as `os_isdir()` on Windows.
+///
+/// @return `true` if `name` is a directory and executable.
+bool os_isdir_executable(const char *name)
+  FUNC_ATTR_NONNULL_ALL
+{
+  int32_t mode = os_getperm((const char *)name);
+  if (mode < 0) {
+    return false;
+  }
+
+#ifdef WIN32
+  return (S_ISDIR(mode));
+#else
+  return (S_ISDIR(mode) && (S_IXUSR & mode));
+#endif
+}
+
 /// Check what `name` is:
 /// @return NODE_NORMAL: file or directory (or doesn't exist)
 ///         NODE_WRITABLE: writable device, socket, fifo, etc.
diff --git a/test/functional/core/job_spec.lua b/test/functional/core/job_spec.lua
index 34168e10c2..eb02610df0 100644
--- a/test/functional/core/job_spec.lua
+++ b/test/functional/core/job_spec.lua
@@ -17,6 +17,7 @@ local pathroot = helpers.pathroot
 local nvim_set = helpers.nvim_set
 local expect_twostreams = helpers.expect_twostreams
 local expect_msg_seq = helpers.expect_msg_seq
+local expect_err = helpers.expect_err
 local Screen = require('test.functional.ui.screen')
 
 -- Kill process with given pid
@@ -115,6 +116,17 @@ describe('jobs', function()
     ok(string.find(err, "E475: Invalid argument: expected valid directory$") ~= nil)
   end)
 
+  it('produces error when using non-executable `cwd`', function()
+    if iswin() then return end  -- N/A for Windows
+
+    local dir = 'Xtest_not_executable_dir'
+    mkdir(dir)
+    funcs.setfperm(dir, 'rw-------')
+    expect_err('E475: Invalid argument: expected valid directory$', nvim,
+               'command', "call jobstart('pwd', {'cwd': '" .. dir .. "'})")
+    rmdir(dir)
+  end)
+
   it('returns 0 when it fails to start', function()
     eq("", eval("v:errmsg"))
     feed_command("let g:test_jobid = jobstart([])")