From: David Laight <David.Laight@ACULAB.COM>
To: 'Dan Carpenter' <dan.carpenter@oracle.com>,
Denis Efremov <efremov@linux.com>
Cc: "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
Jes Sorensen <jes.sorensen@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Hans de Goede <hdegoede@redhat.com>,
Bastien Nocera <hadess@hadess.net>,
Dmitry Vyukov <dvyukov@google.com>,
Larry Finger <Larry.Finger@lwfinger.net>
Subject: RE: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls
Date: Tue, 1 Oct 2019 14:36:09 +0000 [thread overview]
Message-ID: <8d2e8196cae74ec4ae20e9c23e898207@AcuMS.aculab.com> (raw)
In-Reply-To: <20191001135649.GH22609@kadam>
> From: Dan Carpenter
> Sent: 01 October 2019 14:57
> Subject: Re: [PATCH] staging: rtl8723bs: hal: Fix memcpy calls
...
> That's true for glibc memcpy() but not for the kernel memcpy(). In the
> kernel there are lots of places which do a zero size memcpy().
And probably from NULL (or even garbage) pointers.
After all a pointer to the end of an array (a + ARRAY_SIZE(a)) is valid
but must not be dereferenced - so memcpy() can't dereference it's
source address when the length is zero.
> The glibc attitude is "the standard allows us to put knives here" so
> let's put knives everywhere in the path. And the GCC attitude is let's
> silently remove NULL checks instead of just printing a warning that the
> NULL check isn't required... It could really make someone despondent.
gcc is the one that add knives...
This reminds me of me of a compiler that decided to optimise away
checks for function addresses being NULL.
At almost exactly the same time that ELF allowed for undefined weak symbols.
Checking whether a function was actually present was non-trivial.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
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next prev parent reply other threads:[~2019-10-01 14:36 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-30 11:01 [PATCH] staging: rtl8723bs: hal: Fix memcpy calls Denis Efremov
2019-09-30 13:18 ` David Laight
2019-09-30 14:25 ` Denis Efremov
2019-10-01 13:56 ` Dan Carpenter
2019-10-01 14:36 ` David Laight [this message]
2019-10-01 15:13 ` Denis Efremov
2019-10-01 16:00 ` David Laight
2019-10-01 18:58 ` Dan Carpenter
2019-10-01 20:15 ` Denis Efremov
2019-10-09 14:38 ` Dan Carpenter
2019-09-30 15:40 ` Denis Efremov
2019-09-30 13:39 ` Sasha Levin
2019-10-09 9:35 ` Hans de Goede
2019-10-09 10:43 ` Denis Efremov
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