linux-kernel - Re: [PATCH v3 1/1] coresight: tmc: Explicit type conversions to prevent integer overflow

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Date:   Fri, 4 Aug 2023 14:16:30 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Ruidong Tian <tianruidong@...ux.alibaba.com>,
        linux-kernel@...r.kernel.org
Cc:     alexander.shishkin@...ux.intel.com, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, mike.leach@...aro.org,
        james.clark@....com
Subject: Re: [PATCH v3 1/1] coresight: tmc: Explicit type conversions to
 prevent integer overflow

On 04/08/2023 09:15, 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.
> 
> Fixes: 22f429f19c41 ("coresight: etm-perf: Add support for ETR backend")
> Signed-off-by: Ruidong Tian <tianruidong@...ux.alibaba.com>
> Reviewed-by: James Clark <james.clark@....com>
> ---
>   drivers/hwtracing/coresight/coresight-tmc-etf.c | 2 +-
>   drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++--
>   drivers/hwtracing/coresight/coresight-tmc.h     | 2 +-
>   3 files changed, 5 insertions(+), 4 deletions(-)


Added additional Fixes tags as required and pushed it here :

https://git.kernel.org/coresight/c/fd380097cdb3

Thanks!
Suzuki