[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <63a44def-fd5d-4f21-8d09-bb608cfab524@intel.com>
Date: Tue, 1 Jul 2025 17:36:06 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 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>, Alexey Kardashevskiy <aik@....com>, Alexander Shishkin
<alexander.shishkin@...ux.intel.com>
CC: Jonathan Corbet <corbet@....net>, 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>, <linux-mm@...ck.org>
Subject: Re: [PATCHv8 12/17] x86/traps: Communicate a LASS violation in #GP
message
On 7/1/2025 2:58 AM, Kirill A. Shutemov wrote:
> /*
> @@ -672,6 +681,12 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs,
> if (*addr < ~__VIRTUAL_MASK &&
> *addr + insn.opnd_bytes - 1 > __VIRTUAL_MASK)
> return GP_NON_CANONICAL;
> + else if (*addr < ~__VIRTUAL_MASK &&
> + cpu_feature_enabled(X86_FEATURE_LASS)) {
> + if (*addr < PAGE_SIZE)
> + return GP_NULL_POINTER;
> + return GP_LASS_VIOLATION;
> + }
The comments above this section of code say:
/*
* Check that:
* - the operand is not in the kernel half
* - the last byte of the operand is not in the user canonical half
*/
They should be updated since we are updating the logic.
Also, below is easier to read than above:
if (*addr < ~__VIRTUAL_MASK) {
if (*addr + insn.opnd_bytes - 1 > __VIRTUAL_MASK)
return EXC_NON_CANONICAL;
if (cpu_feature_enabled(X86_FEATURE_LASS)) {
if (*addr < PAGE_SIZE)
return EXC_NULL_POINTER;
return EXC_LASS_VIOLATION;
}
}
I am wondering if the NULL pointer exception should be made
unconditional, even if it is unlikely to reach here without LASS. So
maybe something like this:
if (*addr < ~__VIRTUAL_MASK) {
if (*addr + insn.opnd_bytes - 1 > __VIRTUAL_MASK)
return EXC_NON_CANONICAL;
if (*addr < PAGE_SIZE)
return EXC_NULL_POINTER;
if (cpu_feature_enabled(X86_FEATURE_LASS))
return EXC_LASS_VIOLATION;
}
Powered by blists - more mailing lists