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Subject[PATCH 4/7] perf,x86/msr: Fix possible Spectre-v1 for msr
> arch/x86/events/msr.c:178 msr_event_init() warn: potential spectre issue 'msr' (local cap)

Userspace controls @attr, sanitize cfg (attr->config) before using it
to index an array.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/events/msr.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/arch/x86/events/msr.c
+++ b/arch/x86/events/msr.c
@@ -158,9 +158,6 @@ static int msr_event_init(struct perf_ev
if (event->attr.type != event->pmu->type)
return -ENOENT;

- if (cfg >= PERF_MSR_EVENT_MAX)
- return -EINVAL;
-
/* unsupported modes and filters */
if (event->attr.exclude_user ||
event->attr.exclude_kernel ||
@@ -171,6 +168,11 @@ static int msr_event_init(struct perf_ev
event->attr.sample_period) /* no sampling */
return -EINVAL;

+ if (cfg >= PERF_MSR_EVENT_MAX)
+ return -EINVAL;
+
+ cfg = array_index_nospec(cfg, PERF_MSR_EVENT_MAX);
+
if (!msr[cfg].attr)
return -EINVAL;


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