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From: Peter Zijlstra <peterz@infradead.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] perf/core: Fix reversed NULL check in perf_event_groups_less()
Date: Fri, 13 Mar 2020 13:27:25 +0100	[thread overview]
Message-ID: <20200313122725.GZ12561@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200312105637.GA8960@mwanda>

On Thu, Mar 12, 2020 at 01:56:37PM +0300, Dan Carpenter wrote:
> This NULL check is reversed so it leads to a Smatch warning and
> presumably a NULL dereference.
> 
>     kernel/events/core.c:1598 perf_event_groups_less()
>     error: we previously assumed 'right->cgrp->css.cgroup' could be null
> 	(see line 1590)
> 
> Fixes: 95ed6c707f26 ("perf/cgroup: Order events in RB tree by cgroup id")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 6a47c3e54fe9..607c04ec7cfa 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1587,7 +1587,7 @@ perf_event_groups_less(struct perf_event *left, struct perf_event *right)
>  			 */
>  			return true;
>  		}
> -		if (!right->cgrp || right->cgrp->css.cgroup) {
> +		if (!right->cgrp || !right->cgrp->css.cgroup) {
>  			/*
>  			 * Right has no cgroup but left does, no cgroups come
>  			 * first.

Thanks!

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ian Rogers <irogers@google.com>, Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] perf/core: Fix reversed NULL check in perf_event_groups_less()
Date: Fri, 13 Mar 2020 12:27:25 +0000	[thread overview]
Message-ID: <20200313122725.GZ12561@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200312105637.GA8960@mwanda>

On Thu, Mar 12, 2020 at 01:56:37PM +0300, Dan Carpenter wrote:
> This NULL check is reversed so it leads to a Smatch warning and
> presumably a NULL dereference.
> 
>     kernel/events/core.c:1598 perf_event_groups_less()
>     error: we previously assumed 'right->cgrp->css.cgroup' could be null
> 	(see line 1590)
> 
> Fixes: 95ed6c707f26 ("perf/cgroup: Order events in RB tree by cgroup id")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 6a47c3e54fe9..607c04ec7cfa 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1587,7 +1587,7 @@ perf_event_groups_less(struct perf_event *left, struct perf_event *right)
>  			 */
>  			return true;
>  		}
> -		if (!right->cgrp || right->cgrp->css.cgroup) {
> +		if (!right->cgrp || !right->cgrp->css.cgroup) {
>  			/*
>  			 * Right has no cgroup but left does, no cgroups come
>  			 * first.

Thanks!

  reply	other threads:[~2020-03-13 12:27 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-12 10:56 [PATCH] perf/core: Fix reversed NULL check in perf_event_groups_less() Dan Carpenter
2020-03-12 10:56 ` Dan Carpenter
2020-03-13 12:27 ` Peter Zijlstra [this message]
2020-03-13 12:27   ` Peter Zijlstra
2020-03-21  2:24   ` Ian Rogers
2020-03-21  2:24     ` Ian Rogers
2020-03-20 12:58 ` [tip: perf/core] " tip-bot2 for Dan Carpenter

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