linux-kernel - Re: [PATCH] fs: lockd: avoid possible wrong NULL parameter

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Date:   Thu, 3 Aug 2023 11:08:34 +0800
From:   Su Hui <suhui@...china.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     chuck.lever@...cle.com, jlayton@...nel.org, neilb@...e.de,
        kolga@...app.com, Dai.Ngo@...cle.com, tom@...pey.com,
        trond.myklebust@...merspace.com, anna@...nel.org,
        nathan@...nel.org, ndesaulniers@...gle.com, trix@...hat.com,
        bfields@...ldses.org, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] fs: lockd: avoid possible wrong NULL parameter

On 2023/8/2 18:41, Dan Carpenter wrote:
> There was a big fight about memcpy() in 2010.
>
> https://lwn.net/Articles/416821/
>
> It's sort of related but also sort of different.  My understanding is
> that the glibc memcpy() says that memcpy() always does a dereference so
> it can delete all the NULL checks which come after.  The linux kernel
> uses -fno-delete-null-pointer-checks to turn this behavior off.
Really big fight!
This article seems talk about  problem that using memcpy() to copy 
overlapping regions.
I'm not sure glibc memcpy does the check about NULL， but glibc printf 
does this check.
"And GNU libc checks strings passed to printf for a %s placeholder for 
NULL,
when the C standard says this is not allowed."[1]
[1] https://lwn.net/Articles/416821/
>
> regards,
> dan carpenter