Re: [PATCH bpf] bpf: relax zero fixed offset constraint on KF_TRUSTED_ARGS/KF_RCU

[patchwork-bot+netdevbpf@kernel.org]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue,  9 Jul 2024 21:09:39 +0000 you wrote:
> Currently, BPF kfuncs which accept trusted pointer arguments
> i.e. those flagged as KF_TRUSTED_ARGS, KF_RCU, or KF_RELEASE, all
> require an original/unmodified trusted pointer argument to be supplied
> to them. By original/unmodified, it means that the backing register
> holding the trusted pointer argument that is to be supplied to the BPF
> kfunc must have its fixed offset set to zero, or else the BPF verifier
> will outright reject the BPF program load. However, this zero fixed
> offset constraint that is currently enforced by the BPF verifier onto
> BPF kfuncs specifically flagged to accept KF_TRUSTED_ARGS or KF_RCU
> trusted pointer arguments is rather unnecessary, and can limit their
> usability in practice. Specifically, it completely eliminates the
> possibility of constructing a derived trusted pointer from an original
> trusted pointer. To put it simply, a derived pointer is a pointer
> which points to one of the nested member fields of the object being
> pointed to by the original trusted pointer.
> 
> [...]

Here is the summary with links:
  - [bpf] bpf: relax zero fixed offset constraint on KF_TRUSTED_ARGS/KF_RCU
    https://git.kernel.org/bpf/bpf-next/c/605c96997d89

You are awesome, thank you!
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