linux-kernel - Re: [PATCH v2 1/8] x86: vdso: Introduce asm/vdso/mman.h

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: <fe23745e-a965-4b74-863d-9479fdef239f@app.fastmail.com>
Date: Wed, 25 Sep 2024 21:23:21 +0000
From: "Arnd Bergmann" <arnd@...db.de>
To: "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Vincenzo Frascino" <vincenzo.frascino@....com>,
 linux-kernel@...r.kernel.org, Linux-Arch <linux-arch@...r.kernel.org>,
 linux-mm@...ck.org
Cc: "Andy Lutomirski" <luto@...nel.org>,
 "Thomas Gleixner" <tglx@...utronix.de>,
 "Jason A . Donenfeld" <Jason@...c4.com>,
 "Michael Ellerman" <mpe@...erman.id.au>,
 "Nicholas Piggin" <npiggin@...il.com>, "Naveen N Rao" <naveen@...nel.org>,
 "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, "Theodore Ts'o" <tytso@....edu>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Steven Rostedt" <rostedt@...dmis.org>,
 "Masami Hiramatsu" <mhiramat@...nel.org>,
 "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH v2 1/8] x86: vdso: Introduce asm/vdso/mman.h

On Wed, Sep 25, 2024, at 06:51, Christophe Leroy wrote:
> Le 23/09/2024 à 16:19, Vincenzo Frascino a écrit :
>> @@ -0,0 +1,15 @@
>> +
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef __ASM_VDSO_MMAN_H
>> +#define __ASM_VDSO_MMAN_H
>> +
>> +#ifndef __ASSEMBLY__
>> +
>> +#include <uapi/linux/mman.h>
>> +
>> +#define VDSO_MMAP_PROT	PROT_READ | PROT_WRITE
>> +#define VDSO_MMAP_FLAGS	MAP_DROPPABLE | MAP_ANONYMOUS
>
> I still can't see the point with that change.
>
> Today 4 architectures implement getrandom and none of them require that 
> indirection. Please leave prot and flags as they are in the code.
>
> Then this file is totally pointless, VDSO code can include 
> uapi/linux/mman.h directly.
>
> VDSO is userland code, it should be safe to include any UAPI file there.

I think we are hitting an unfortunate corner case in the build
system here, based on the way we handle the uapi/ file namespace
in the kernel:

include/uapi/linux/mman.h includes three headers: asm/mman.h,
asm-generic/hugetlb_encode.h and linux/types.h. Two of these
exist in both include/uapi/ and include/, so while building
kernel code we end up picking up the non-uapi version which
on some architectures includes many other headers.

I agree that moving the contents out of uapi/ into vdso/ namespace
is not a solution here because that removes the contents from
the installed user headers, but we still need to do something
to solve the issue.

The easiest workaround I see for this particular file is to
move the contents of arch/{arm,arm64,parisc,powerpc,sparc,x86}/\
include/asm/mman.h into a different file to ensure that the
only existing file is the uapi/ one. Unfortunately this does
not help to avoid it regressing again in the future.

To go a little step further I would also move
uapi/asm-generic/hugetlb_encode.h to uapi/linux/hugetlb_encode.h
or merge it into uapi/linux/mman.h. This file has no business
in asm-generic/* since there is only one copy.

After looking at this file for way too long, I somehow
ended up with a (completely unrelated) cleanup series that
I now posted at
https://lore.kernel.org/lkml/20240925210615.2572360-1-arnd@kernel.org/T/#t

     Arnd