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SubjectRe: [PATCH v2] coresight: tmc: Explicit type conversions to prevent integer overflow
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On 03/08/2023 03:33, Ruidong Tian wrote:
> 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@linux.alibaba.com>
> Reviewed-by: James Clark <james.clark@arm.com>

Fixes: 22f429f19c41 ("coresight: etm-perf: Add support for ETR backend")


> ---
> 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);

There are other places where such a fix is needed.
e.g.,

$ git grep "nr_pages << PAGE_SHIFT"
drivers/hwtracing/coresight/coresight-tmc*
drivers/hwtracing/coresight/coresight-tmc-etf.c: head =
handle->head & ((buf->nr_pages << PAGE_SHIFT) - 1);
drivers/hwtracing/coresight/coresight-tmc-etr.c:#define
PERF_IDX2OFF(idx, buf) ((idx) % ((buf)->nr_pages << PAGE_SHIFT))
drivers/hwtracing/coresight/coresight-tmc-etr.c: if ((nr_pages <<
PAGE_SHIFT) > drvdata->size) {
drivers/hwtracing/coresight/coresight-tmc-etr.c: etr_buf
= tmc_alloc_etr_buf(drvdata, (nr_pages << PAGE_SHIFT),
drivers/hwtracing/coresight/coresight-tmc.h: return
sg_table->data_pages.nr_pages << PAGE_SHIFT;

Are you able to fix all of them ?

Suzuki

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