linux-kernel - Re: [PATCH v5 00/16] Enable Linear Address Space Separation support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87plnit616.fsf@ubik.fi.intel.com>
Date: Wed, 30 Oct 2024 09:16:05 +0200
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave
 Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H. Peter Anvin"
 <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>, Ard Biesheuvel
 <ardb@...nel.org>, "Paul E. McKenney" <paulmck@...nel.org>, Josh Poimboeuf
 <jpoimboe@...nel.org>, Xiongwei Song <xiongwei.song@...driver.com>, Xin Li
 <xin3.li@...el.com>, "Mike Rapoport (IBM)" <rppt@...nel.org>, Brijesh
 Singh <brijesh.singh@....com>, Michael Roth <michael.roth@....com>, Tony
 Luck <tony.luck@...el.com>, "Kirill A. Shutemov"
 <kirill.shutemov@...ux.intel.com>, Alexey Kardashevskiy <aik@....com>,
 Jonathan Corbet <corbet@....net>, Sohil Mehta <sohil.mehta@...el.com>,
 Ingo Molnar <mingo@...nel.org>, Pawan Gupta
 <pawan.kumar.gupta@...ux.intel.com>, Daniel Sneddon
 <daniel.sneddon@...ux.intel.com>, Kai Huang <kai.huang@...el.com>,
 Sandipan Das <sandipan.das@....com>, Breno Leitao <leitao@...ian.org>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>, Alexei Starovoitov
 <ast@...nel.org>, Hou Tao <houtao1@...wei.com>, Juergen Gross
 <jgross@...e.com>, Vegard Nossum <vegard.nossum@...cle.com>, Kees Cook
 <kees@...nel.org>, Eric Biggers <ebiggers@...gle.com>, Jason Gunthorpe
 <jgg@...pe.ca>, "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Andrew
 Morton <akpm@...ux-foundation.org>, Luis Chamberlain <mcgrof@...nel.org>,
 Yuntao Wang <ytcoode@...il.com>, Rasmus Villemoes
 <linux@...musvillemoes.dk>, Christophe Leroy
 <christophe.leroy@...roup.eu>, Tejun Heo <tj@...nel.org>, Changbin Du
 <changbin.du@...wei.com>, Huang Shijie <shijie@...amperecomputing.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>, Namhyung Kim
 <namhyung@...nel.org>, Arnaldo Carvalho de Melo <acme@...hat.com>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-efi@...r.kernel.org, alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH v5 00/16] Enable Linear Address Space Separation support

Matthew Wilcox <willy@...radead.org> writes:

> On Mon, Oct 28, 2024 at 06:07:48PM +0200, Alexander Shishkin wrote:
> I lack the wit to read & understand these patches to answer this
> question, so I'll just ask it:

I was hoping they are readable and straightforward. Please, do point out
things that are not so, or not explained well enough, I'll fix them.

> What happens when the kernel does a NULL pointer dereference (due to a
> bug)?  It's not an attempt to access userspace, but it should result in
> a good bug report.  Normally this would be outside a STAC/CLAC region,
> but I suppose technically it could be within one.

Outside of STAC/CLAC there will be a message, see 13/16 or [0].  It
doesn't have helpful things like "if (address < PAGE_SIZE) printk("NULL
ptr deref\n);", but since it prints the address, I assumed it was
sufficient. Does this sound reasonable? Or is it preferrable to make it
look exactly like the !LASS NULL dereference?

Inside STAC/CLAC it should trigger a regular page fault and all the
error messages that result from it.

[0] https://lore.kernel.org/all/20241028160917.1380714-14-alexander.shishkin@linux.intel.com/

Thanks,
--
Alex