Commit ef9ee4ad authored Apr 20, 2018 by Peter Zijlstra Committed by Ingo Molnar May 05, 2018

perf/x86: Fix possible Spectre-v1 indexing for hw_perf_event cache_*



> arch/x86/events/core.c:319 set_ext_hw_attr() warn: potential spectre issue 'hw_cache_event_ids[cache_type]' (local cap)
> arch/x86/events/core.c:319 set_ext_hw_attr() warn: potential spectre issue 'hw_cache_event_ids' (local cap)
> arch/x86/events/core.c:328 set_ext_hw_attr() warn: potential spectre issue 'hw_cache_extra_regs[cache_type]' (local cap)
> arch/x86/events/core.c:328 set_ext_hw_attr() warn: potential spectre issue 'hw_cache_extra_regs' (local cap)

Userspace controls @config which contains 3 (byte) fields used for a 3
dimensional array deref.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 4411ec1d

arch/x86/events/core.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -307,14 +307,17 @@ set_ext_hw_attr(struct hw_perf_event hwc, struct perf_event event)
		cache_type = (config >> 0) & 0xff;
		if (cache_type >= PERF_COUNT_HW_CACHE_MAX)
		return -EINVAL;
		cache_type = array_index_nospec(cache_type, PERF_COUNT_HW_CACHE_MAX);

		cache_op = (config >> 8) & 0xff;
		if (cache_op >= PERF_COUNT_HW_CACHE_OP_MAX)
		return -EINVAL;
		cache_op = array_index_nospec(cache_op, PERF_COUNT_HW_CACHE_OP_MAX);

		cache_result = (config >> 16) & 0xff;
		if (cache_result >= PERF_COUNT_HW_CACHE_RESULT_MAX)
		return -EINVAL;
		cache_result = array_index_nospec(cache_result, PERF_COUNT_HW_CACHE_RESULT_MAX);

		val = hw_cache_event_ids[cache_type][cache_op][cache_result];