Re: [PATCH] tracing/filters: Check perf permissions before resolving .function

[Kyle Zeng]

On Wed, Oct 07, 2026 at 05:52:22AM +0000, Masami Hiramatsu wrote:
> On Tue, 06 Oct 2026 20:47:17 -0700, Kyle Zeng <kylebot@xxxxxxxxxx> wrote:
> > On Wed, Oct 07, 2026 at 03:44:20AM +0000, Masami Hiramatsu wrote:
> > > On Tue, 06 Oct 2026 15:51:12 -0700, Kyle Zeng <kylebot@xxxxxxxxxx> wrote:
> > > > perf_trace_event_perm() allows tracepoint counters that do not request
> > > > PERF_SAMPLE_RAW without raw tracepoint permissions. A self-targeted,
> > > > disabled event with exclude_kernel=1 can therefore reach the filter
> > > > compiler even at perf_event_paranoid=2.
> > > >
> > > > The .function suffix accepts any field of sizeof(long) and resolves its
> > > > operand through kallsyms_lookup_name() and kallsyms_lookup_size_offset().
> > > > The success or failure of a numeric filter discloses whether an address
> > > > belongs to a known kernel symbol range. On x86-64 this can be used to
> > > > recover the randomized kernel image base. A named filter also exposes
> > > > the resolved symbol range through the counter when the tracepoint field
> > > > is controlled by the caller, as with a syscall argument.
> > > >
> > > > Pass the filter's perf origin to the predicate parser and require
> > > > perf_allow_tracepoint() before resolving a .function operand. This uses
> > > > the same sysctl, initial-namespace capability and LSM policy as raw
> > > > tracepoint access, and closes both the numeric and named-symbol oracles.
> > > > Do not change ordinary perf counting filters or filters created through
> > > > the separately controlled tracefs interfaces.
> > > 
> > > Good catch!
> > > 
> > > >
> > > > Fixes: e6745a4da964 ("tracing: Add a way to filter function addresses to function names")
> > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > Assisted-by: Codex:gpt-6-astra
> > > 
> > > nit: This should be 
> > > 
> > > Assisted-by: LLM
> >
> > Didn't know there was a change of convention. Should I send in a v2 or
> > it will be picked up automatically?
> 
> We can change the tag when picking up, so you don't need to resend it only
> for tag update. But for this patch, please update according to Sashiko's
> comment.

Thanks for the explanation.
I just sent a v2: https://sashiko.dev/#/message/20261007050315.65139-1-kylebot%40openai.com

Best,
Kyle

> 
>  https://lore.kernel.org/all/sashiko-outbox-162502@xxxxxxxxxx/
> 
> Thanks,
> 
> >
> > Thanks,
> > Kyle
> >
> > > 
> > > > Signed-off-by: Kyle Zeng <kylebot@xxxxxxxxxx>
> > > 
> > > Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> > > 
> > > Thanks!
> > > 
> > > 
> > > -- 
> > > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>