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To: "De Lara Guarch, Pablo" <pablo.de.lara.guarch@intel.com>,
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From: Andy Green <andy@warmcat.com>
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Date: Sat, 12 May 2018 09:33:17 +0800
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Subject: Re: [dpdk-dev] [PATCH v4 16/18] app/proc-info: sprintf overrun bug
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On 05/11/2018 08:26 PM, De Lara Guarch, Pablo wrote:
>
>
>> -----Original Message-----
>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Andy Green
>> Sent: Friday, May 11, 2018 2:47 AM
>> To: dev@dpdk.org
>> Subject: [dpdk-dev] [PATCH v4 16/18] app/proc-info: sprintf overrun bug
>>
>> /home/agreen/projects/dpdk/app/proc-info/main.c: In function
>> ‘nic_xstats_display’:
>> /home/agreen/projects/dpdk/app/proc-info/main.c:495:45:
>> error: ‘%s’ directive writing up to 255 bytes into a region of size between 165
>> and 232 [-Werror=format-overflow=]
>> sprintf(buf, "PUTVAL %s/dpdkstat-port.%u/%s-%s N:%"
>> ^~
>> PRIu64"\n", host_id, port_id, counter_type,
>> ~~~~~~~~~~~~
>> /home/agreen/projects/dpdk/app/proc-info/main.c:495:4: note:
>> ‘sprintf’ output between 31 and 435 bytes into a destination of size 256
>> sprintf(buf, "PUTVAL %s/dpdkstat-port.%u/%s-%s N:%"
>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> PRIu64"\n", host_id, port_id, counter_type,
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> xstats_names[i].name, values[i]);
>>
>> Signed-off-by: Andy Green <andy@warmcat.com>
>> ---
>> app/proc-info/main.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/app/proc-info/main.c b/app/proc-info/main.c index
>> 539e13243..df46c235e 100644
>> --- a/app/proc-info/main.c
>> +++ b/app/proc-info/main.c
>> @@ -488,14 +488,19 @@ nic_xstats_display(uint16_t port_id)
>> if (enable_collectd_format) {
>> char counter_type[MAX_STRING_LEN];
>> char buf[MAX_STRING_LEN];
>> + size_t n;
>>
>> collectd_resolve_cnt_type(counter_type,
>> sizeof(counter_type),
>> xstats_names[i].name);
>> - sprintf(buf, "PUTVAL %s/dpdkstat-port.%u/%s-%s N:%"
>> + n = snprintf(buf, MAX_STRING_LEN,
>> + "PUTVAL %s/dpdkstat-port.%u/%s-%s N:%"
>> PRIu64"\n", host_id, port_id, counter_type,
>> xstats_names[i].name, values[i]);
>> - ret = write(stdout_fd, buf, strlen(buf));
>> + buf[sizeof(buf) - 1] = '\0';
>
> No need to NULL terminate, since snprintf already does it.
OK.
>> + if (n > sizeof(buf) - 1)
>> + n = sizeof(buf) - 1;
>
> If (n > sizeof(buf) -1 ), it means that there wasn't enough space to write all the data,
> So shouldn't we return an error here?
It's just logging stuff, policy about truncated overlength logs could go
either way.
Prior to this patch its policy was to corrupt your stack if overlength
;-) so I think it's moving it on in the right direction merely
truncating it.
-Andy
>> + ret = write(stdout_fd, buf, n);
>> if (ret < 0)
>> goto err;
>> } else {
>
> Missing fixes line and CC stable.
>
> Fixes: 2deb6b5246d7 ("app/procinfo: add collectd format and host id")
> Cc: stable@dpdk.org
>