Re: [PATCH] perf/core: Require kernel access for page-size samples

[sashiko-bot@kernel.org]

> PERF_SAMPLE_CODE_PAGE_SIZE and PERF_SAMPLE_DATA_PAGE_SIZE translate a
> sampled virtual address using the current task's page tables, including
> kernel mappings.  exclude_kernel only filters the execution mode of the
> sample; it does not establish that the address being translated belongs
> to userspace.
> 
> For example, an unprivileged tracer can put a kernel address in a
> tracee's saved IP at a syscall-entry stop.  A following syscall perf
> tracepoint still sees user-mode registers and reports the page size at
> that address.  The distinction between unmapped and mapped addresses
> can disclose the randomized kernel image base even at
> perf_event_paranoid=2.
> 
> Require perf_allow_kernel() for both page-size sample types, as is
> already done for PERF_SAMPLE_PHYS_ADDR.  This applies the existing perf
> and LSM authorization policy before the event is created, independently
> of the source or representation of the sampled address.  Authorized
> page-size sampling and events that do not request these translation
> fields are unchanged.
> 
> Fixes: 8d97e71811aa ("perf/core: Add PERF_SAMPLE_DATA_PAGE_SIZE")
> Fixes: 995f088efebe ("perf/core: Add support for PERF_SAMPLE_CODE_PAGE_SIZE")
> Assisted-by: Codex:gpt-6-astra
> Signed-off-by: Kyle Zeng <kylebot@openai.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006225033.53296-1-kylebot@openai.com?part=1