On Fri, Feb 9, 2024 at 5:22 AM Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote: > > Adds a wrapper around `kuid_t` called `Kuid`. This allows us to define > various operations on kuids such as equality and current_euid. It also > lets us provide conversions from kuid into userspace values. > > Rust Binder needs these operations because it needs to compare kuids for > equality, and it needs to tell userspace about the pid and uid of > incoming transactions. > > To read kuids from a `struct task_struct`, you must currently use > various #defines that perform the appropriate field access under an RCU > read lock. Currently, we do not have a Rust wrapper for rcu_read_lock, > which means that for this patch, there are two ways forward: > > 1. Inline the methods into Rust code, and use __rcu_read_lock directly > rather than the rcu_read_lock wrapper. This gives up lockdep for > these usages of RCU. > > 2. Wrap the various #defines in helpers and call the helpers from Rust. > > This patch uses the second option. One possible disadvantage of the > second option is the possible introduction of speculation gadgets, but > as discussed in [1], the risk appears to be acceptable. > > Of course, once a wrapper for rcu_read_lock is available, it is > preferable to use that over either of the two above approaches. Is this worth a FIXME? > Link: https://lore.kernel.org/all/202312080947.674CD2DC7@keescook/ [1] > Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx> > Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@xxxxxxxxx> > Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> Reviewed-by: Trevor Gross <tmgross@xxxxxxxxx>
