linux-kernel - Re: [PATCH 1/2] pipe: fix potential use-after-free in pipe

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Message-ID: <YZJbBNs/63pnXngK@casper.infradead.org>
Date:   Mon, 15 Nov 2021 13:05:08 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] pipe: fix potential use-after-free in pipe_read()

On Mon, Nov 15, 2021 at 02:13:44PM +0800, Leizhen (ThunderTown) wrote:
> 
> 
> On 2021/11/15 12:25, Matthew Wilcox wrote:
> > On Mon, Nov 15, 2021 at 11:57:20AM +0800, Zhen Lei wrote:
> >>  			if (!buf->len) {
> >> +				unsigned int __maybe_unused flags = buf->flags;
> > 
> > Why __maybe_unused?
> 
> It's used only if "#ifdef CONFIG_WATCH_QUEUE". Otherwise, a warning will be reported.

Better to turn the #ifdef into if (IS_ENABLED())