From: David Laight <David.Laight@ACULAB.COM>
To: 'Linus Torvalds' <torvalds@linux-foundation.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
"bp@alien8.de" <bp@alien8.de>,
Josh Poimboeuf <jpoimboe@kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@kernel.org>,
Mikel Rychliski <mikel@mikelr.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: RE: [PATCH] x86: Allow user accesses to the base of the guard page
Date: Sun, 24 Nov 2024 10:28:17 +0000 [thread overview]
Message-ID: <90e813acc14848b1aa0995578f80ffad@AcuMS.aculab.com> (raw)
In-Reply-To: <CAHk-=whsUQMM-FszR-D+myn9-B2pDidXG9DQWGKfAhU3azX==g@mail.gmail.com>
From: Linus Torvalds
> Sent: 23 November 2024 23:45
>
> On Sat, 23 Nov 2024 at 14:36, David Laight <David.Laight@aculab.com> wrote:
> >
> > The problem is that it is valid to pass a buffer that ends right
> > at the end of valid user memory.
>
> There's a difference between "valid" and "we care".
>
> This is way past that case. The only possible reason for that
> zero-byte thing at the end of the address space is somebody actively
> looking for some edge case, not a real use.
Mikel gave the exact test that was failing.
I should have been more clear that the issue is fixing valid transfers
that end at the end of valid memory without breaking zero length
transfers anywhere else.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2024-11-24 10:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-23 18:48 David Laight
2024-11-23 19:02 ` Linus Torvalds
2024-11-23 22:36 ` David Laight
2024-11-23 23:44 ` Linus Torvalds
2024-11-24 0:24 ` Mikel Rychliski
2024-11-24 0:30 ` Linus Torvalds
2024-11-24 3:10 ` Mikel Rychliski
2024-11-24 10:28 ` David Laight [this message]
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