jai.git

index d7dab25..a460637 100644
--- a/fs.cc
+++ b/fs.cc
@@ -148,9 +148,10 @@ xmnt_propagate(int fd, std::uint64_t propagation, bool recursive)
   xmnt_setattr(fd, a, recursive ? AT_RECURSIVE : 0);
 }
 
-void
+bool
 recursive_umount(const path &tree, bool detach)
 {
+  bool ret = true;
   auto mps = mountpoints();
   auto dirs = subtree_rev(mps, tree);
   for (const auto &dir : dirs) {
@@ -158,8 +159,11 @@ recursive_umount(const path &tree, bool detach)
       warn(R"(umount("{}"): {})", dir.string(), strerror(errno));
       if (detach && umount2(dir.c_str(), UMOUNT_NOFOLLOW | MNT_DETACH) == 0)
         warn("did lazy unmount of {}\n", dir.string());
+      else
+        ret = false;
     }
   }
+  return ret;
 }
 
 bool

index 7c0b72d..09bfa49 100644
--- a/fs.h
+++ b/fs.h
@@ -114,7 +114,7 @@ make_tmpfs(const char *source, Opt... opt)
   return make_mount(*conf);
 }
 
-void recursive_umount(const path &tree, bool detach = true);
+bool recursive_umount(const path &tree, bool detach = true);
 
 enum class FollowLinks {
   kNoFollow = 0,
@@ -196,12 +196,11 @@ xopenat(int dfd, const path &file, int flags, mode_t mode = 0755)
 }
 
 inline Fd
-xdup(int fd)
+xdup(int fd, int minfd = 3)
 {
-  auto ret = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+  auto ret = fcntl(fd, F_DUPFD_CLOEXEC, minfd);
   if (ret == -1)
-    syserr("F_DUPFD_CLOEXEC");
-  fcntl(ret, F_SETFD, 1);
+    syserr("{}: F_DUPFD_CLOEXEC", fdpath(fd));
   return ret;
 }
 

index 4a3e952..cc70496 100644
--- a/jai.cc
+++ b/jai.cc
@@ -5,8 +5,10 @@
 #include "options.h"
 
 #include <cassert>
+#include <cstdlib>
 #include <cstring>
 #include <filesystem>
+#include <linux/prctl.h>
 #include <print>
 
 #include <acl/libacl.h>
@@ -45,6 +47,9 @@ struct Config {
   Fd run_jai_fd_;
   Fd run_jai_user_fd_;
 
+  // Hold some file descriptors to prevent unmounting
+  std::vector<Fd> mp_holder_;
+
   PathSet config_loop_detect_;
 
   void init_credentials();
@@ -375,6 +380,7 @@ Config::make_idmap_ns()
   });
   auto pfds = xpipe();
   if (!(pid = xfork(CLONE_NEWUSER))) {
+    prctl(PR_SET_PDEATHSIG, SIGKILL);
     pfds[1].reset();
     char c;
     read(*pfds[0], &c, 1);
@@ -418,13 +424,13 @@ Config::make_mnt_ns()
       .attr_set = MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV,
       .propagation = MS_PRIVATE,
   };
-  Fd tmp = clone_tree(*make_private_tmp());
+  Fd tmp = clone_tree(*mp_holder_.emplace_back(make_private_tmp()));
 
   Fd home;
   Fd mapns;
   Credentials *sbcred = &user_cred_;
   if (mode_ == kCasual)
-    home = clone_tree(*make_home_overlay());
+    home = clone_tree(*mp_holder_.emplace_back(make_home_overlay()));
   else {
     if (mode_ == kStrict) {
       sbcred = &untrusted_cred_;
@@ -555,7 +561,8 @@ Config::unmountall()
 
   auto dir = xopendir(run_jai_user());
   while (auto de = readdir(dir))
-    unlinkat(run_jai_user(), de->d_name, AT_REMOVEDIR);
+    if (unlinkat(run_jai_user(), de->d_name, AT_REMOVEDIR) && errno == ENOTDIR)
+      unlinkat(run_jai_user(), de->d_name, 0);
 
   // Get rid of any stale files the user can't delete
   try {
@@ -638,16 +645,32 @@ Config::exec(int nsfd, char **argv)
   if (auto pid = xfork()) {
     close(nsfd);
     int status = -1;
-    while (waitpid(pid, &status, 0) == -1 && errno == EINTR)
-      ;
-    // unmount();
-    if (WIFEXITED(status))
-      exit(WEXITSTATUS(status));
-    if (WIFSIGNALED(status)) {
-      signal(WTERMSIG(status), SIG_DFL);
-      raise(WTERMSIG(status));
+    for (;;) {
+      int r = waitpid(pid, &status, WUNTRACED);
+      std::println(stderr, "waitpid -> pid = {}, status = 0x{:x}", r, status);
+      if (r != pid) {
+        if (r == -1 && errno != EINTR)
+          syserr("waitpid");
+      }
+      else if (WIFSTOPPED(status)) {
+        // Because the child is in its own PID namespace, it cannot
+        // stop us if it tries to suspend the process group.  Hence,
+        // detect if the child stopped and stop ourselves.
+        if (int sig = WSTOPSIG(status); sig == SIGSTOP || sig == SIGTSTP ||
+                                        sig == SIGTTIN || sig == SIGTTOU)
+          raise(sig);
+      }
+      else {
+        // unmount();
+        if (WIFEXITED(status))
+          exit(WEXITSTATUS(status));
+        if (WIFSIGNALED(status)) {
+          signal(WTERMSIG(status), SIG_DFL);
+          raise(WTERMSIG(status));
+        }
+        err("unknown child wait status 0x{:x}", status);
+      }
     }
-    _exit(1);
   }
 
   try {
@@ -847,9 +870,17 @@ main(int argc, char **argv)
   else
     prog = PACKAGE_TARNAME;
 
+#if 1
+  using ToCatch = std::exception;
+#else
+  struct ToCatch {
+    auto what() const { return ""; }
+  };
+#endif
+
   try {
     do_main(argc, argv);
-  } catch (const std::exception &e) {
+  } catch (const ToCatch &e) {
     warn("{}", e.what());
     return 1;
   }