perf: Require kernel access for text poke events

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Perf events with exclude_kernel=1 can be opened without kernel perf
access. However, exclude_kernel does not suppress text-poke sideband
records. Every PERF_RECORD_TEXT_POKE is marked PERF_RECORD_MISC_KERNEL
and contains a raw kernel instruction address.

An unprivileged task can therefore open and mmap a task-local software
event with text_poke=1. Both opening a count-only tracepoint event and
configuring UDP GRO for ESP-in-UDP cause updates to inline static calls;
the observer receives the relocated addresses of the modified instructions.
For a known kernel image, any such address reveals the runtime kernel
text base despite KASLR.

Call perf_allow_kernel() whenever attr.text_poke is set, regardless of
exclude_kernel. Events that neither monitor kernel execution nor request
text-poke records retain their existing permissions.

Fixes: e17d43b93e ("perf: Add perf text poke event")
Assisted-by: LLM
Signed-off-by: Zhengchuan Liang <zcliangcn@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/99131354c41e23188f778b92f90363775b482395.1790573390.git.zcliangcn@gmail.com

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Zhengchuan Liang 2026-09-28 10:59:35 -07:00 • committed by Peter Zijlstra

parent b9d1fdc6f4

commit 357e8a77a5

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kernel/events/core.c

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