perf/core: Add RCU read lock protection to perf_iterate_ctx()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: perf/core: Add RCU read lock protection to perf_iterate_ctx() The perf_iterate_ctx() function performs RCU list traversal but currently lacks RCU read lock protection. This causes lockdep warnings when running perf probe with unshare(1) under CONFIG_PROVE_RCU_LIST=y: WARNING: suspicious RCU usage kernel/events/core.c:8168 RCU-list traversed in non-reader section!! Call Trace: lockdep_rcu_suspicious ? perf_event_addr_filters_apply perf_iterate_ctx perf_event_exec begin_new_exec ? load_elf_phdrs load_elf_binary ? lock_acquire ? find_held_lock ? bprm_execve bprm_execve do_execveat_common.isra.0 __x64_sys_execve do_syscall_64 entry_SYSCALL_64_after_hwframe This protection was previously present but was removed in commit bd2756811766 ("perf: Rewrite core context handling"). Add back the necessary rcu_read_lock()/rcu_read_unlock() pair around perf_iterate_ctx() call in perf_event_exec(). [ mingo: Use scoped_guard() as suggested by Peter ]

References

• https://git.kernel.org/stable/c/f390c2eea571945f357a2d3b9fcb1c015767132e
• https://git.kernel.org/stable/c/a2475ccad6120546ea45dbcd6cd1f74dc565ef6b
• https://git.kernel.org/stable/c/dd536566dda9a551fc2a2acfab5313a5bb13ed02
• https://git.kernel.org/stable/c/0fe8813baf4b2e865d3b2c735ce1a15b86002c74