From: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org,
linux-kernel@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Stephen Boyd <swboyd@chromium.org>,
Ingo Molnar <mingo@redhat.com>,
Namhyung Kim <namhyung@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
linux-arm-kernel@lists.infradead.org,
Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf()
Date: Thu, 22 Oct 2020 19:53:32 +0530 [thread overview]
Message-ID: <8ecb29f116a78855ca59928c1e0e1eb7@codeaurora.org> (raw)
In-Reply-To: <20201022133414.GH2611@hirez.programming.kicks-ass.net>
On 2020-10-22 19:04, Peter Zijlstra wrote:
> On Thu, Oct 22, 2020 at 06:19:37PM +0530, Sai Prakash Ranjan wrote:
>> On 2020-10-22 17:02, Peter Zijlstra wrote:
>> > On Thu, Oct 22, 2020 at 04:27:52PM +0530, Sai Prakash Ranjan wrote:
>> >
>> > > Looking at the ETR and other places in the kernel, ETF and the
>> > > ETB are the only places trying to dereference the task(owner)
>> > > in tmc_enable_etf_sink_perf() which is also called from the
>> > > sched_in path as in the call trace.
>> >
>> > > @@ -391,6 +392,10 @@ static void *tmc_alloc_etf_buffer(struct
>> > > coresight_device *csdev,
>> > > {
>> > > int node;
>> > > struct cs_buffers *buf;
>> > > + struct task_struct *task = READ_ONCE(event->owner);
>> > > +
>> > > + if (!task || is_kernel_event(event))
>> > > + return NULL;
>> >
>> >
>> > This is *wrong*... why do you care about who owns the events?
>> >
>>
>> The original issue was the owner being NULL and causing
>> a NULL pointer dereference. I did ask some time back
>> if it is valid for the owner to be NULL [1] and should
>> probably be handled in events core?
>
> No, what I asked is why do you care about ->owner to begin with? That
> seems wrong. A driver should not touch ->owner _at_all_.
>
Ah ok, so Suzuki explained that in other reply and if there is
some other better way?
Thanks,
Sai
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next prev parent reply other threads:[~2020-10-22 14:25 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 10:57 [PATCHv2 0/4] coresight: etf/etb10/etr: Fix NULL pointer dereference crashes Sai Prakash Ranjan
2020-10-22 10:57 ` [PATCHv2 1/4] perf/core: Export is_kernel_event() Sai Prakash Ranjan
2020-10-22 10:57 ` [PATCHv2 2/4] coresight: tmc-etf: Fix NULL ptr dereference in tmc_enable_etf_sink_perf() Sai Prakash Ranjan
2020-10-22 11:32 ` Peter Zijlstra
2020-10-22 12:49 ` Sai Prakash Ranjan
2020-10-22 13:34 ` Peter Zijlstra
2020-10-22 14:23 ` Sai Prakash Ranjan [this message]
2020-10-22 13:30 ` Suzuki Poulose
2020-10-22 15:06 ` Peter Zijlstra
2020-10-22 15:32 ` Suzuki Poulose
2020-10-22 21:20 ` Mathieu Poirier
2020-10-23 7:39 ` Peter Zijlstra
2020-10-23 8:49 ` Suzuki Poulose
2020-10-23 9:23 ` Peter Zijlstra
2020-10-23 10:49 ` Suzuki Poulose
2020-10-23 9:41 ` Peter Zijlstra
2020-10-23 10:34 ` Suzuki Poulose
2020-10-23 10:54 ` Peter Zijlstra
2020-10-23 12:56 ` Suzuki Poulose
2020-10-23 13:16 ` Peter Zijlstra
2020-10-23 13:29 ` Suzuki Poulose
2020-10-23 13:44 ` Peter Zijlstra
2020-10-23 20:37 ` Mathieu Poirier
2020-10-30 7:59 ` Sai Prakash Ranjan
2020-10-30 16:48 ` Mathieu Poirier
2020-10-30 17:26 ` Sai Prakash Ranjan
2020-11-04 17:03 ` Mathieu Poirier
2020-10-22 10:57 ` [PATCHv2 3/4] coresight: etb10: Fix possible NULL ptr dereference in etb_enable_perf() Sai Prakash Ranjan
2020-10-22 10:57 ` [PATCHv2 4/4] coresight: tmc-etr: Fix possible NULL ptr dereference in get_perf_etr_buf_cpu_wide() Sai Prakash Ranjan
2020-10-22 11:10 ` [PATCHv2 0/4] coresight: etf/etb10/etr: Fix NULL pointer dereference crashes Sai Prakash Ranjan
2020-10-22 11:23 ` Sai Prakash Ranjan
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