1 files changed, 16 insertions, 13 deletions
diff --git a/test/syscalls/linux/dup.cc b/test/syscalls/linux/dup.cc
index fca0880a6..8f0974f45 100644
--- a/test/syscalls/linux/dup.cc
+++ b/test/syscalls/linux/dup.cc
@@ -101,18 +101,16 @@ TEST(DupTest, Dup2) {
 }
 
 TEST(DupTest, Rlimit) {
-  constexpr int kFDLimit = 101;
   auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
 
   struct rlimit rl = {};
   EXPECT_THAT(getrlimit(RLIMIT_NOFILE, &rl), SyscallSucceeds());
 
-  // Lower the rlimit first, as it may be equal to /proc/sys/fs/nr_open, in
-  // which case even users with CAP_SYS_RESOURCE can't raise it.
-  rl.rlim_cur = kFDLimit * 2;
   ASSERT_THAT(setrlimit(RLIMIT_NOFILE, &rl), SyscallSucceeds());
 
+  constexpr int kFDLimit = 101;
+  // Create a file descriptor that will be above the limit.
   FileDescriptor aboveLimitFD =
       ASSERT_NO_ERRNO_AND_VALUE(Dup2(fd, kFDLimit * 2 - 1));
 
@@ -121,19 +119,24 @@ TEST(DupTest, Rlimit) {
   ASSERT_THAT(dup3(fd.get(), kFDLimit, 0), SyscallFails());
 
   std::vector<std::unique_ptr<FileDescriptor>> fds;
-  int prev = fd.get();
-  for (int i = 0; i < kFDLimit; i++) {
-    int d = dup(fd.get());
-    if (d == -1) {
+  int prev_fd = fd.get();
+  int used_fds = 0;
+  for (int i = 0; i < kFDLimit; ++i) {
+    int new_fd = dup(fd.get());
+    if (new_fd == -1) {
       break;
     }
-    std::unique_ptr<FileDescriptor> f = absl::make_unique<FileDescriptor>(d);
-    EXPECT_LT(d, kFDLimit);
-    EXPECT_GT(d, prev);
-    prev = d;
+    auto f = absl::make_unique<FileDescriptor>(new_fd);
+    EXPECT_LT(new_fd, kFDLimit);
+    EXPECT_GT(new_fd, prev_fd);
+    // Check that all fds in (prev_fd, new_fd) are used.
+    for (int j = prev_fd + 1; j < new_fd; ++j) {
+      if (fcntl(j, F_GETFD) != -1) used_fds++;
+    }
+    prev_fd = new_fd;
     fds.push_back(std::move(f));
   }
-  EXPECT_EQ(fds.size(), kFDLimit - fd.get() - 1);
+  EXPECT_EQ(fds.size() + used_fds, kFDLimit - fd.get() - 1);
 }
 
 TEST(DupTest, Dup2SameFD) {