perf: Require kernel access for text poke events

Overview

In the Linux kernel, the following vulnerability has been resolved:

perf: Require kernel access for text poke events

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.

Affected

• Linux >= e17d43b93e544f5016c0251d2074c15568d5d963 < 8473f44db9f710ea6f8cafb22f2e3ba6cb8ca9a7
• Linux >= e17d43b93e544f5016c0251d2074c15568d5d963 < e506333d1b9f42f1e402acebf1283af3c44a3809
• Linux >= e17d43b93e544f5016c0251d2074c15568d5d963 < 677d0b51ac1a0db55d768c4c6399210b3de0795b
• Linux >= e17d43b93e544f5016c0251d2074c15568d5d963 < 357e8a77a501d96c9517f01f4a211eed5e9c9184
• Linux 5.9

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.