linux-kernel - Re: [RFC PATCH] perf/core: Prevent dereferencing NULL pointer

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Message-ID: <20250206080520.GG7145@noisy.programming.kicks-ass.net>
Date: Thu, 6 Feb 2025 09:05:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: I Hsin Cheng <richard120310@...il.com>
Cc: mark.rutland@....com, mingo@...hat.com, acme@...nel.org,
	namhyung@...nel.org, alexander.shishkin@...ux.intel.com,
	jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, jserv@...s.ncku.edu.tw,
	shuah@...nel.org
Subject: Re: [RFC PATCH] perf/core: Prevent dereferencing NULL pointer

On Thu, Feb 06, 2025 at 03:06:08AM +0800, I Hsin Cheng wrote:
> According to coverity scan check, there's possible cases where
> "ring_buffer_get()" returns a NULL in "perf_mmap_close".

That makes no sense. Having a mmap should pin the buffer.

> Use a "BUG_ON()" to check for NULL pointer existence, panic if it does
> exist, otherwise it's safe to dereference "rb" and access its members.

How the hell is a BUG_ON() any better than a NULL deref?