linux-perf-users.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexander Antonov <alexander.antonov@linux.intel.com>
To: "Liang, Kan" <kan.liang@linux.intel.com>,
	13145886936@163.com, tglx@linutronix.de, bp@alien8.de,
	x86@kernel.org
Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	gushengxian <gushengxian@yulong.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] x86: eas should not be NULL when it is referenced
Date: Fri, 25 Jun 2021 17:26:18 +0300	[thread overview]
Message-ID: <ba5f35f9-5ed0-b6be-4e19-45fef717a160@linux.intel.com> (raw)
In-Reply-To: <7d4862ae-7ac6-11e8-5c8d-74610eabd5b5@linux.intel.com>


On 6/25/2021 5:11 PM, Liang, Kan wrote:
>
>
> On 6/25/2021 9:33 AM, Alexander Antonov wrote:
>> Hello Kan,
>>> On 6/24/2021 3:03 PM, Liang, Kan wrote:
>>>> I think the NULL pointer dereference of eas should not happen, 
>>>> because die is -1 if eas is NULL. But the whole error handling path 
>>>> looks fragile.
>>>>
>>>> We already fixed one issue caused by it in commit ID f797f05d917f 
>>>> ("perf/x86/intel/uncore: Fix for iio mapping on Skylake Server")
>>>> https://lore.kernel.org/lkml/160149233331.7002.10919231011379055356.tip-bot2@tip-bot2/ 
>>>>
>>>>
>>>> Maybe something as below?
>>>>
>>>>  From 3de81ba3b04262ef3346297d82f6c4ffb4af7029 Mon Sep 17 00:00:00 
>>>> 2001
>>>> From: Kan Liang <kan.liang@linux.intel.com>
>>>> Date: Thu, 24 Jun 2021 11:17:57 -0700
>>>> Subject: [PATCH] perf/x86/intel/uncore: Clean up error handling 
>>>> path of iio mapping
>>>>
>>>> The error handling path of iio mapping looks fragile. We already fixed
>>>> one issue caused by it, commit ID f797f05d917f 
>>>> ("perf/x86/intel/uncore:
>>>> Fix for iio mapping on Skylake Server"). Clean up the error handling
>>>> path and make the code robust.
>> I didn't catch why does the current error handling path look fragile?
>> Are there cases when it works incorrect?
>>
>
>
> I don't think it causes any severe problem for now, e.g., crash, 
> because current code checks die before the dereference.
> But I think it violates the Linux kernel coding style (one err bug) 
> and may bring potential issues.
>
> https://www.kernel.org/doc/html/v4.10/process/coding-style.html
>
> Thanks,
> Kan

OK,
Thank you for the explanation.

- Alexander
>
>> Thanks,
>> Alexander
>>>>
>>>> Reported-by: gushengxian <gushengxian@yulong.com>
>>>> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
>>>> ---
>>>>   arch/x86/events/intel/uncore_snbep.c | 6 ++++--
>>>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/x86/events/intel/uncore_snbep.c 
>>>> b/arch/x86/events/intel/uncore_snbep.c
>>>> index 7622762..6d4a5a9 100644
>>>> --- a/arch/x86/events/intel/uncore_snbep.c
>>>> +++ b/arch/x86/events/intel/uncore_snbep.c
>>>> @@ -3802,11 +3802,11 @@ pmu_iio_set_mapping(struct 
>>>> intel_uncore_type *type, struct attribute_group *ag)
>>>>       /* One more for NULL. */
>>>>       attrs = kcalloc((uncore_max_dies() + 1), sizeof(*attrs), 
>>>> GFP_KERNEL);
>>>>       if (!attrs)
>>>> -        goto err;
>>>> +        goto clear_topology;
>>>>
>>>>       eas = kcalloc(uncore_max_dies(), sizeof(*eas), GFP_KERNEL);
>>>>       if (!eas)
>>>> -        goto err;
>>>> +        goto clear_attrs;
>>>>
>>>>       for (die = 0; die < uncore_max_dies(); die++) {
>>>>           sprintf(buf, "die%ld", die);
>>>> @@ -3827,7 +3827,9 @@ pmu_iio_set_mapping(struct intel_uncore_type 
>>>> *type, struct attribute_group *ag)
>>>>       for (; die >= 0; die--)
>>>>           kfree(eas[die].attr.attr.name);
>>>>       kfree(eas);
>>>> +clear_attrs:
>>>>       kfree(attrs);
>>>> +clear_topology:
>>>>       kfree(type->topology);
>>>>   clear_attr_update:
>>>>       type->attr_update = NULL;

      reply	other threads:[~2021-06-25 14:26 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24  7:04 13145886936
2021-06-24  7:24 ` Peter Zijlstra
2021-06-24 19:03 ` Liang, Kan
2021-06-24 19:06   ` Liang, Kan
2021-06-25 13:33     ` Alexander Antonov
2021-06-25 14:11       ` Liang, Kan
2021-06-25 14:26         ` Alexander Antonov [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=ba5f35f9-5ed0-b6be-4e19-45fef717a160@linux.intel.com \
    --to=alexander.antonov@linux.intel.com \
    --cc=13145886936@163.com \
    --cc=bp@alien8.de \
    --cc=gushengxian@yulong.com \
    --cc=kan.liang@linux.intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-perf-users@vger.kernel.org \
    --cc=peterz@infradead.org \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH] x86: eas should not be NULL when it is referenced' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).