linux-hardening - Re: [PATCH] x86/uaccess: Fix missed zeroing of ia32 u64 get

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Message-ID: <CABVgOSnk3Uq1HjNgV=ATjO455PDv-W6-hDjqGyscp=ybc7U3Qg@mail.gmail.com>
Date: Tue, 11 Jun 2024 14:14:07 +0800
From: David Gow <davidgow@...gle.com>
To: Kees Cook <kees@...nel.org>
Cc: 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>, Sean Christopherson <seanjc@...gle.com>, Peter Zijlstra <peterz@...radead.org>, 
	Arnd Bergmann <arnd@...db.de>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
	Qiuxu Zhuo <qiuxu.zhuo@...el.com>, Nadav Amit <nadav.amit@...il.com>, 
	Masahiro Yamada <masahiroy@...nel.org>, Christian Brauner <brauner@...nel.org>, 
	David Howells <dhowells@...hat.com>, Uros Bizjak <ubizjak@...il.com>, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] x86/uaccess: Fix missed zeroing of ia32 u64 get_user()
 range checking

On Tue, 11 Jun 2024 at 05:02, Kees Cook <kees@...nel.org> wrote:
>
> When reworking the range checking for get_user(), the get_user_8() case
> on 32-bit wasn't zeroing the high register. (The jump to bad_get_user_8
> was accidentally dropped.) Restore the correct error handling
> destination (and rename the jump to using the expected ".L" prefix).
>
> While here, switch to using a named argument ("size") for the call
> template ("%c4" to "%c[size]") as already used in the other call
> templates in this file.
>
> Found after moving the usercopy selftests to KUnit:
>
>       # usercopy_test_invalid: EXPECTATION FAILED at
>       lib/usercopy_kunit.c:278
>       Expected val_u64 == 0, but
>           val_u64 == -60129542144 (0xfffffff200000000)
>
> Reported-by: David Gow <davidgow@...gle.com>
> Closes: https://lore.kernel.org/all/CABVgOSn=tb=Lj9SxHuT4_9MTjjKVxsq-ikdXC4kGHO4CfKVmGQ@mail.gmail.com
> Fixes: b19b74bc99b1 ("x86/mm: Rework address range check in get_user() and put_user()")
> Signed-off-by: Kees Cook <kees@...nel.org>
> ---
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: x86@...nel.org
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> Cc: Nadav Amit <nadav.amit@...il.com>
> Cc: Masahiro Yamada <masahiroy@...nel.org>
> ---

Thanks: this fixes it here, both under qemu and on real hardware.

Tested-by: David Gow <davidgow@...gle.com>

-- David

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