On Sun, Sep 15, 2024 at 10:24 PM Kees Cook <kees@xxxxxxxxxx> wrote: > > On Sun, Sep 15, 2024 at 02:31:30PM +0000, Alice Ryhl wrote: > > From: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > > > > Add a wrapper around `struct cred` called `Credential`, and provide > > functionality to get the `Credential` associated with a `File`. > > > > Rust Binder must check the credentials of processes when they attempt to > > perform various operations, and these checks usually take a > > `&Credential` as parameter. The security_binder_set_context_mgr function > > would be one example. This patch is necessary to access these security_* > > methods from Rust. > > > > This Rust abstraction makes the following assumptions about the C side: > > * `struct cred` is refcounted with `get_cred`/`put_cred`. > > Yes > > > * It's okay to transfer a `struct cred` across threads, that is, you do > > not need to call `put_cred` on the same thread as where you called > > `get_cred`. > > Yes > > > * The `euid` field of a `struct cred` never changes after > > initialization. > > "after initialization", yes. The bprm cred during exec is special in > that it gets updated (bprm_fill_uid) before it is installed into current > via commit_creds() in begin_new_exec() (the point of no return for > exec). I think it will be pretty normal to need different Rust types for pre- and post-initialization of a C value. When a value is not yet fully initialized, you usually get some extra powers (modify otherwise immutable fields), but probably also lose some powers (you can't share it with other threads yet). I can document that this type should not be used with the bprm cred during exec. > > * The `f_cred` field of a `struct file` never changes after > > initialization. > > Yes. > > > > > Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > > Co-developed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> > > Reviewed-by: Trevor Gross <tmgross@xxxxxxxxx> > > Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx> > > Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx> > > Reviewed-by: Gary Guo <gary@xxxxxxxxxxx> > > Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> > > Reviewed-by: Kees Cook <kees@xxxxxxxxxx> Thanks for the review! Alice
