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>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index a6006e7bb729..b1be0ac51ce0 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -304,17 +304,20 @@ set_ext_hw_attr(struct hw_perf_event *hwc, struct perf_event *event)
 
         config = attr->config;
 
-        cache_type = (config >>  0) & 0xff;
+        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];