linux-kernel - [PATCH rust-next 1/2] rust: miscdevice: add llseek support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250818135846.133722-2-ryasuoka@redhat.com>
Date: Mon, 18 Aug 2025 22:58:38 +0900
From: Ryosuke Yasuoka <ryasuoka@...hat.com>
To: arnd@...db.de,
	gregkh@...uxfoundation.org,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	dakr@...nel.org,
	lee@...nel.org
Cc: Ryosuke Yasuoka <ryasuoka@...hat.com>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH rust-next 1/2] rust: miscdevice: add llseek support

Add the ability to write a file_operations->llseek hook in Rust when
using the miscdevice abstraction.

Signed-off-by: Ryosuke Yasuoka <ryasuoka@...hat.com>
---
 rust/kernel/miscdevice.rs | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index 6373fe183b27..597e7b66e493 100644
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -125,6 +125,16 @@ fn release(device: Self::Ptr, _file: &File) {
         drop(device);
     }
 
+    /// Handler for llseek.
+    fn llseek(
+        _device: <Self::Ptr as ForeignOwnable>::Borrowed<'_>,
+        _file: &File,
+        _offset: i64,
+        _whence: i32,
+    ) -> Result<isize> {
+        build_error!(VTABLE_DEFAULT_ERROR)
+    }
+
     /// Handle for mmap.
     ///
     /// This function is invoked when a user space process invokes the `mmap` system call on
@@ -245,6 +255,27 @@ impl<T: MiscDevice> MiscdeviceVTable<T> {
         0
     }
 
+    /// # Safety
+    ///
+    /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
+    unsafe extern "C" fn llseek(file: *mut bindings::file, offset: i64, whence: c_int) -> i64 {
+        // SAFETY: The llseek call of a file can access the private data.
+        let private = unsafe { (*file).private_data };
+        // SAFETY: This is a Rust Miscdevice, so we call `into_foreign` in `open` and
+        // `from_foreign` in `release`, and `fops_llseek` is guaranteed to be called between those
+        // two operations.
+        let device = unsafe { <T::Ptr as ForeignOwnable>::borrow(private) };
+        // SAFETY:
+        // * The file is valid for the duration of this call.
+        // * There is no active fdget_pos region on the file on this thread.
+        let file = unsafe { File::from_raw_file(file) };
+
+        match T::llseek(device, file, offset, whence) {
+            Ok(res) => res as i64,
+            Err(err) => i64::from(err.to_errno()),
+        }
+    }
+
     /// # Safety
     ///
     /// `file` must be a valid file that is associated with a `MiscDeviceRegistration<T>`.
@@ -340,6 +371,11 @@ impl<T: MiscDevice> MiscdeviceVTable<T> {
     const VTABLE: bindings::file_operations = bindings::file_operations {
         open: Some(Self::open),
         release: Some(Self::release),
+        llseek: if T::HAS_LLSEEK {
+            Some(Self::llseek)
+        } else {
+            None
+        },
         mmap: if T::HAS_MMAP { Some(Self::mmap) } else { None },
         unlocked_ioctl: if T::HAS_IOCTL {
             Some(Self::ioctl)
-- 
2.50.1