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Message-ID: <20231201104831.2195715-1-aliceryhl@google.com>
Subject: Re: [PATCH 3/7] rust: security: add abstraction for secctx
From:   Alice Ryhl <aliceryhl@google.com>
To:     benno.lossin@proton.me
Cc:     a.hindborg@samsung.com, alex.gaynor@gmail.com,
        aliceryhl@google.com, arve@android.com, bjorn3_gh@protonmail.com,
        boqun.feng@gmail.com, brauner@kernel.org, cmllamas@google.com,
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Benno Lossin <benno.lossin@proton.me> writes:
> On 11/29/23 14:11, Alice Ryhl wrote:
>> +    /// Returns the bytes for this security context.
>> +    pub fn as_bytes(&self) -> &[u8] {
>> +        let mut ptr = self.secdata;
>> +        if ptr.is_null() {
>> +            // Many C APIs will use null pointers for strings of length zero, but
> 
> I would just write that the secctx API uses null pointers to denote a
> string of length zero.

I don't actually know whether it can ever be null, I just wanted to stay
on the safe side.

>> +            // `slice::from_raw_parts` doesn't allow the pointer to be null even if the length is
>> +            // zero. Replace the pointer with a dangling but non-null pointer in this case.
>> +            debug_assert_eq!(self.seclen, 0);
> 
> I am feeling a bit uncomfortable with this, why can't we just return
> an empty slice in this case?

I can do that, but to be clear, what I'm doing here is also definitely
okay.

Alice