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

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Date:   Fri, 4 Aug 2023 11:06:51 +0800
From:   Ruidong Tian <tianruidong@...ux.alibaba.com>
To:     Suzuki K Poulose <suzuki.poulose@....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, james.clark@....com
Subject: Re: [PATCH v2] coresight: tmc: Explicit type conversions to prevent
 integer overflow

Sure, I will put them all to patch v3.

Ruidong

On 2023/8/4 00:19, Suzuki K Poulose wrote:
> 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@...ux.alibaba.com>
>> Reviewed-by: James Clark <james.clark@....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