[PATCH 0/2] perf: Fix overflow in PERF_IDX2OFF() for Arm SPE and TRBE drivers

[PATCH 0/2] perf: Fix overflow in PERF_IDX2OFF() for Arm SPE and TRBE drivers

[Leo Yan]

If the AUX buffer size is specified as 2 GiB or larger, the expression
"(buf)->nr_pages << PAGE_SHIFT" may exceed 0x8000_0000. Since
(buf)->nr_pages is a signed integer, the shift can overflow and produce
a negative value. As a result, PERF_IDX2OFF() fails to work correctly.

Fix this by casting (buf)->nr_pages to unsigned long before the shift,
which allows PERF_IDX2OFF() to handle large buffers properly.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
Leo Yan (2):
      coresight: trbe: Prevent overflow in PERF_IDX2OFF()
      perf: arm_spe: Prevent overflow in PERF_IDX2OFF()

 drivers/hwtracing/coresight/coresight-trbe.c | 3 ++-
 drivers/perf/arm_spe_pmu.c                   | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)
---
base-commit: 5aca7966d2a7255ba92fd5e63268dd767b223aa5
change-id: 20250917-fix_aux_trace_index-9745674f5061

Best regards,
-- 
Leo Yan <leo.yan@arm.com>

[PATCH 1/2] coresight: trbe: Prevent overflow in PERF_IDX2OFF()

[Leo Yan]

Cast nr_pages to unsigned long to avoid overflow when handling large
AUX buffer sizes (>= 2 GiB).

Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver")
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 drivers/hwtracing/coresight/coresight-trbe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 8267dd1a2130d37d9507791620ea7bc8cbcd675c..8f426f94e32a15fd26e6c4e42385a5d93a7b7c1a 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -23,7 +23,8 @@
 #include "coresight-self-hosted-trace.h"
 #include "coresight-trbe.h"
 
-#define PERF_IDX2OFF(idx, buf) ((idx) % ((buf)->nr_pages << PAGE_SHIFT))
+#define PERF_IDX2OFF(idx, buf) \
+	((idx) % ((unsigned long)(buf)->nr_pages << PAGE_SHIFT))
 
 /*
  * A padding packet that will help the user space tools

-- 
2.34.1

[PATCH 2/2] perf: arm_spe: Prevent overflow in PERF_IDX2OFF()

[Leo Yan]

Cast nr_pages to unsigned long to avoid overflow when handling large
AUX buffer sizes (>= 2 GiB).

Fixes: d5d9696b0380 ("drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension")
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 drivers/perf/arm_spe_pmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 369e77ad5f13ffb490bf8f128fee5180d1254bc6..8f14cb324e018349fbe19c5c20d92a9cdcfd2e73 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -97,7 +97,8 @@ struct arm_spe_pmu {
 #define to_spe_pmu(p) (container_of(p, struct arm_spe_pmu, pmu))
 
 /* Convert a free-running index from perf into an SPE buffer offset */
-#define PERF_IDX2OFF(idx, buf)	((idx) % ((buf)->nr_pages << PAGE_SHIFT))
+#define PERF_IDX2OFF(idx, buf) \
+	((idx) % ((unsigned long)(buf)->nr_pages << PAGE_SHIFT))
 
 /* Keep track of our dynamic hotplug state */
 static enum cpuhp_state arm_spe_pmu_online;

-- 
2.34.1

Re: [PATCH 0/2] perf: Fix overflow in PERF_IDX2OFF() for Arm SPE and TRBE drivers

[Will Deacon]

On Wed, 17 Sep 2025 18:41:37 +0100, Leo Yan wrote:
> If the AUX buffer size is specified as 2 GiB or larger, the expression
> "(buf)->nr_pages << PAGE_SHIFT" may exceed 0x8000_0000. Since
> (buf)->nr_pages is a signed integer, the shift can overflow and produce
> a negative value. As a result, PERF_IDX2OFF() fails to work correctly.
> 
> Fix this by casting (buf)->nr_pages to unsigned long before the shift,
> which allows PERF_IDX2OFF() to handle large buffers properly.
> 
> [...]

Applied to will (for-next/perf), thanks!

[1/2] coresight: trbe: Prevent overflow in PERF_IDX2OFF()
      https://git.kernel.org/will/c/105f56877f2d
[2/2] perf: arm_spe: Prevent overflow in PERF_IDX2OFF()
      https://git.kernel.org/will/c/a29fea30dd93

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev