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Subject[tip: perf/urgent] perf/x86: Fix potential out-of-bounds access
The following commit has been merged into the perf/urgent branch of tip:

Commit-ID: 1e69a0efc0bd0e02b8327e7186fbb4a81878ea0b
Gitweb: https://git.kernel.org/tip/1e69a0efc0bd0e02b8327e7186fbb4a81878ea0b
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 06 Dec 2019 12:50:16 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 17 Dec 2019 13:32:46 +01:00

perf/x86: Fix potential out-of-bounds access

UBSAN reported out-of-bound accesses for x86_pmu.event_map(), it's
arguments should be < x86_pmu.max_events. Make sure all users observe
this constraint.

Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Meelis Roos <mroos@linux.ee>
---
arch/x86/events/core.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index 9a89d98..84fe1be 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1642,9 +1642,12 @@ static struct attribute_group x86_pmu_format_group __ro_after_init = {

ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr, char *page)
{
- struct perf_pmu_events_attr *pmu_attr = \
+ struct perf_pmu_events_attr *pmu_attr =
container_of(attr, struct perf_pmu_events_attr, attr);
- u64 config = x86_pmu.event_map(pmu_attr->id);
+ u64 config = 0;
+
+ if (pmu_attr->id < x86_pmu.max_events)
+ config = x86_pmu.event_map(pmu_attr->id);

/* string trumps id */
if (pmu_attr->event_str)
@@ -1713,6 +1716,9 @@ is_visible(struct kobject *kobj, struct attribute *attr, int idx)
{
struct perf_pmu_events_attr *pmu_attr;

+ if (idx >= x86_pmu.max_events)
+ return 0;
+
pmu_attr = container_of(attr, struct perf_pmu_events_attr, attr.attr);
/* str trumps id */
return pmu_attr->event_str || x86_pmu.event_map(idx) ? attr->mode : 0;
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