linux-kernel - Re: [PATCH] perf probe: convert_name_to_addr() allocated the wrong size buffer for a function name

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Date:	Tue, 16 Oct 2012 17:13:46 +0900
From:	Hyeoncheol Lee <hyc.lee@...il.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	acme@...stprotocols.net, LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH] perf probe: convert_name_to_addr() allocated the wrong
 size buffer for a function name

Hi,

2012/10/16 Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>:
> (2012/10/16 10:37), Hyeoncheol Lee wrote:
>> convert_name_to_addr() allocated sizeof(char *) * MAX_PROBE_ARGS
>> bytes for a function name
>
> Yeah, that one was from my laziness...
>
>>
>> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>> Signed-off-by: Hyeoncheol Lee <hyc.lee@...il.com>
>> ---
>>  tools/perf/util/probe-event.c |    5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>> index 49a256e..bb40ed4 100644
>> --- a/tools/perf/util/probe-event.c
>> +++ b/tools/perf/util/probe-event.c
>> @@ -2352,13 +2352,14 @@ static int convert_name_to_addr(struct perf_probe_event *pev, const char *exec)
>>               free(exec_copy);
>>       }
>>       free(pp->function);
>> -     pp->function = zalloc(sizeof(char *) * MAX_PROBE_ARGS);
>> +     pp->function = zalloc(sizeof(char) *
>> +                           (3 + sizeof(unsigned long long) * 2));
>
> Could you comment that this is enough long here?
>

Because a hexadecimal address that starts with "0x"
will be stored in pp->function. sizeof(unsigned long long) * 2 is
maximum length of hexadecimal number of  variable "vaddr"
and 3 bytes are for "0x" and null character.

>>       if (!pp->function) {
>>               ret = -ENOMEM;
>>               pr_warning("Failed to allocate memory by zalloc.\n");
>>               goto out;
>>       }
>> -     e_snprintf(pp->function, MAX_PROBE_ARGS, "0x%llx", vaddr);
>> +     sprintf(pp->function, "0x%llx", vaddr);
>
> And at least we should use snprintf instead of sprintf...
> (I think ret = e_snprintf(...) is better)
>

You are right, but I didn't want to write down the length of
"pp->function" again.

>>       ret = 0;
>>
>>  out:
>>
>
> Thank you,
>
> --
> Masami HIRAMATSU
> IT Management Research Dept. Linux Technology Center
> Hitachi, Ltd., Yokohama Research Laboratory
> E-mail: masami.hiramatsu.pt@...achi.com
>
>

Thank you very much!
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