linux-kernel - Re: [PATCH] perf: increase size of buf in perf_evsel__hists

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Message-ID: <2032D1DB-821B-4B6B-882C-0E77E5582D5F@fb.com>
Date:   Sun, 1 Nov 2020 18:06:41 +0000
From:   Song Liu <songliubraving@...com>
To:     David Laight <David.Laight@...LAB.COM>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        "Arnaldo Carvalho de Melo" <acme@...nel.org>
Subject: Re: [PATCH] perf: increase size of buf in perf_evsel__hists_browse()



> On Oct 31, 2020, at 4:27 AM, David Laight <David.Laight@...LAB.COM> wrote:
> 
> From: Song Liu
>> Sent: 30 October 2020 23:55
>> 
>> Making perf with gcc-9.1.1 generates the following warning:
>> 
>>  CC       ui/browsers/hists.o
>> ui/browsers/hists.c: In function 'perf_evsel__hists_browse':
>> ui/browsers/hists.c:3078:61: error: '%d' directive output may be \
>> truncated writing between 1 and 11 bytes into a region of size \
>> between 2 and 12 [-Werror=format-truncation=]
>> 
>> 3078 |       "Max event group index to sort is %d (index from 0 to %d)",
>>      |                                                             ^~
>> ui/browsers/hists.c:3078:7: note: directive argument in the range [-2147483648, 8]
>> 3078 |       "Max event group index to sort is %d (index from 0 to %d)",
>>      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> In file included from /usr/include/stdio.h:937,
>>                 from ui/browsers/hists.c:5:
>> 
>> IOW, the string in line 3078 might be too long for buf[] of 64 bytes.
>> 
>> Fix this by increasing the size of buf[] to 128.
> 
> ISTM that something should be unsigned so that the bound check
> that puts an upper bound of 8 implies a lower bound.
> 
> 	David

Changing both "%d" in this line to "%u" does fix the warning. But we 
are printing "evsel->core.nr_members - 1" here, and nr_members is 
signed int. So I feel more comfortable keep the "%d"s and increase 
the buffer size. 

Thanks,
Song