linux-kernel - Re: [PATCH] uaccess: rust: add strncpy_from

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: <aAtZZgeF5GKdPcaB@google.com>
Date: Fri, 25 Apr 2025 09:44:06 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <benno.lossin@...ton.me>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uaccess: rust: add strncpy_from_user

On Thu, Apr 24, 2025 at 06:32:08PM +0200, Danilo Krummrich wrote:
> On Thu, Apr 24, 2025 at 03:17:48PM +0000, Alice Ryhl wrote:
> > 
> > +/// Reads a nul-terminated string into `buf` and returns the length.
> > +///
> > +/// Fails with [`EFAULT`] if the read happens on a bad address. If the end of `buf` is reached,
> > +/// then the buffer will not be nul-terminated.
> > +#[inline]
> > +pub fn strncpy_from_user(ptr: UserPtr, buf: &mut [u8]) -> Result<usize> {
> 
> Should probably be named strcpy_from_user() instead.

See my reply to Boqun.

> > +    // CAST: Slice lengths are guaranteed to be `<= isize::MAX`.
> > +    let len = buf.len() as isize;
> > +
> > +    // SAFETY: `buf` is valid for writing `buf.len()` bytes.
> > +    let res = unsafe {
> > +        bindings::strncpy_from_user(
> > +            buf.as_mut_ptr(),
> > +            ptr as *const u8,
> 
> kernel::ffi::c_char should always match u8, but should we use the FFI type
> regardless?

Hmm. Should we? I don't mind changing it, but I guess this could be an
interesting discussion point.

Alice