From e16699ddf8fb7004c33c4f4e8ea065553c291a6c Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Sun, 26 Jul 2026 14:08:36 +0200
Subject: kernel: fail early on removed device I/O

---
 kernel/kernel/filesystem/device_inode.cpp          | 10 ++++
 .../filesystem/open_file_descriptor.tests.cpp      | 60 ++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/kernel/kernel/filesystem/device_inode.cpp b/kernel/kernel/filesystem/device_inode.cpp
index 4dcff4a1..4696504e 100644
--- a/kernel/kernel/filesystem/device_inode.cpp
+++ b/kernel/kernel/filesystem/device_inode.cpp
@@ -41,6 +41,11 @@ namespace kernel::filesystem
   auto device_inode::read(void * buffer, kstd::units::bytes offset, kstd::units::bytes size) const
       -> kstd::result<kstd::units::bytes>
   {
+    if (m_device->state() == kapi::devices::state::removed)
+    {
+      return kstd::failure(vfs_errc::no_such_device);
+    }
+
     if (auto block_device =
             kapi::devices::facet_registry::get().resolve<kapi::filesystem::block_special_file>(*m_device))
     {
@@ -53,6 +58,11 @@ namespace kernel::filesystem
   auto device_inode::write(void const * buffer, kstd::units::bytes offset, kstd::units::bytes size)
       -> kstd::result<kstd::units::bytes>
   {
+    if (m_device->state() == kapi::devices::state::removed)
+    {
+      return kstd::failure(vfs_errc::no_such_device);
+    }
+
     if (auto block_device =
             kapi::devices::facet_registry::get().resolve<kapi::filesystem::block_special_file>(*m_device))
     {
diff --git a/kernel/kernel/filesystem/open_file_descriptor.tests.cpp b/kernel/kernel/filesystem/open_file_descriptor.tests.cpp
index 6653ed86..b2d8fb17 100644
--- a/kernel/kernel/filesystem/open_file_descriptor.tests.cpp
+++ b/kernel/kernel/filesystem/open_file_descriptor.tests.cpp
@@ -1,13 +1,19 @@
 #include <kernel/filesystem/open_file_descriptor.hpp>
 
+#include <kernel/devices/storage.hpp>
 #include <kernel/filesystem/dentry.hpp>
+#include <kernel/filesystem/device_inode.hpp>
 #include <kernel/filesystem/inode.hpp>
 #include <kernel/filesystem/vfs.hpp>
 #include <kernel/test_support/filesystem/inode.hpp>
+#include <kernel/test_support/filesystem/storage_boot_module_fixture.hpp>
 #include <kernel/test_support/filesystem/storage_boot_module_vfs_fixture.hpp>
 
+#include <kapi/devices.hpp>
+
 #include <kstd/memory.hpp>
 #include <kstd/print.hpp>
+#include <kstd/system_error.hpp>
 #include <kstd/units.hpp>
 #include <kstd/vector.hpp>
 
@@ -19,6 +25,8 @@
 
 using namespace kstd::units_literals;
 
+// NOLINTBEGIN(readability-magic-numbers)
+
 SCENARIO("Open file descriptor construction", "[filesystem][open_file_descriptor]")
 {
   GIVEN("a dentry and an open file descriptor for that dentry")
@@ -136,3 +144,55 @@ SCENARIO_METHOD(kernel::tests::filesystem::storage_boot_module_vfs_fixture, "Ope
     }
   }
 }
+
+SCENARIO_METHOD(kernel::tests::filesystem::storage_boot_module_fixture, "Open file descriptor handles device removal",
+                "[filesystem][open_file_descriptor]")
+{
+  GIVEN("A file descriptor open on a bound, published devices")
+  {
+    setup_modules(1);
+
+    auto device = kernel::devices::storage::determine_boot_device();
+    REQUIRE(device);
+
+    auto weak_reference = kstd::weak_ptr{device};
+
+    auto device_inode = kstd::make_shared<kernel::filesystem::device_inode>(device);
+    auto dentry = kstd::make_shared<kernel::filesystem::dentry>(nullptr, device_inode, "ram0");
+    auto fd = kstd::make_shared<kernel::filesystem::open_file_descriptor>(dentry);
+
+    device.reset();
+    REQUIRE_FALSE(weak_reference.expired());
+
+    WHEN("the device is removed while the descriptor is still open")
+    {
+      auto locked = weak_reference.lock();
+      REQUIRE(locked);
+      REQUIRE(kapi::devices::remove_device(*locked));
+      locked.reset();
+
+      THEN("the device is kept alive through the file descriptor")
+      {
+        REQUIRE_FALSE(weak_reference.expired());
+      }
+
+      THEN("reading through the file descriptor fails with 'no such device'")
+      {
+        auto buffer = kstd::vector<std::byte>(10);
+        auto bytes_read = fd->read(buffer.data(), kstd::units::bytes{buffer.size()});
+
+        REQUIRE(bytes_read.error() == kstd::errc::no_such_device);
+      }
+
+      THEN("writing through the file descriptor fails with 'no such device'")
+      {
+        auto buffer = kstd::vector<std::byte>(10);
+        auto bytes_written = fd->write(buffer.data(), kstd::units::bytes{buffer.size()});
+
+        REQUIRE(bytes_written.error() == kstd::errc::no_such_device);
+      }
+    }
+  }
+}
+
+// NOLINTEND(readability-magic-numbers)
\ No newline at end of file
-- 
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