linux-kernel - [PATCH v2] coresight: tmc: Explicit type conversions to prevent integer overflow

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Message-Id: <20230803023321.111078-1-tianruidong@linux.alibaba.com>
Date:   Thu,  3 Aug 2023 10:33:21 +0800
From:   Ruidong Tian <tianruidong@...ux.alibaba.com>
To:     tianruidong@...ux.alibaba.com
Cc:     alexander.shishkin@...ux.intel.com, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mike.leach@...aro.org, suzuki.poulose@....com, james.clark@....com
Subject: [PATCH v2] coresight: tmc: Explicit type conversions to prevent integer overflow

Perf cs_etm session executed unexpectedly when AUX buffer > 1G.

  perf record -C 0 -m ,2G -e cs_etm// -- <workload>
  [ perf record: Captured and wrote 2.615 MB perf.data ]

Perf only collect about 2M perf data rather than 2G. This is becasuse
the operation, "nr_pages << PAGE_SHIFT", in coresight tmc driver, will
overflow when nr_pages >= 0x80000(correspond to 1G AUX buffer). The
overflow cause buffer allocation to fail, and TMC driver will alloc
minimal buffer size(1M). You can just get about 2M perf data(1M AUX
buffer + perf data header) at least.

Explicit convert nr_pages to 64 bit to avoid overflow.

Signed-off-by: Ruidong Tian <tianruidong@...ux.alibaba.com>
Reviewed-by: James Clark <james.clark@....com>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 2 +-
 drivers/hwtracing/coresight/coresight-tmc.h     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 766325de0e29..1425ecd1cf78 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1267,7 +1267,7 @@ alloc_etr_buf(struct tmc_drvdata *drvdata, struct perf_event *event,
 	 * than the size requested via sysfs.
 	 */
 	if ((nr_pages << PAGE_SHIFT) > drvdata->size) {
-		etr_buf = tmc_alloc_etr_buf(drvdata, (nr_pages << PAGE_SHIFT),
+		etr_buf = tmc_alloc_etr_buf(drvdata, ((ssize_t)nr_pages << PAGE_SHIFT),
 					    0, node, NULL);
 		if (!IS_ERR(etr_buf))
 			goto done;
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index b97da39652d2..0ee48c5ba764 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -325,7 +325,7 @@ ssize_t tmc_sg_table_get_data(struct tmc_sg_table *sg_table,
 static inline unsigned long
 tmc_sg_table_buf_size(struct tmc_sg_table *sg_table)
 {
-	return sg_table->data_pages.nr_pages << PAGE_SHIFT;
+	return (unsigned long)sg_table->data_pages.nr_pages << PAGE_SHIFT;
 }
 
 struct coresight_device *tmc_etr_get_catu_device(struct tmc_drvdata *drvdata);
-- 
2.33.1