linux-kernel - [PATCH v2 5/6] x86/uaccess: Add user pointer masking to copy_to

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Message-ID: <6500dcd8e7700b4dfe5de4f82ed2da19edc23c58.1729201904.git.jpoimboe@kernel.org>
Date: Thu, 17 Oct 2024 14:55:24 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Waiman Long <longman@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Mark Rutland <mark.rutland@....com>,
	"Kirill A . Shutemov" <kirill@...temov.name>
Subject: [PATCH v2 5/6] x86/uaccess: Add user pointer masking to copy_to_user()

Add user pointer masking to copy_to_user() to mitigate Spectre v1.

A write in a mispredicted access_ok() branch to a user-controlled kernel
address can populate the rest of the affected cache line with kernel
data.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/include/asm/uaccess_64.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 61693028ea2b..0587830a47e1 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -140,6 +140,7 @@ raw_copy_from_user(void *dst, const void __user *src, unsigned long size)
 static __always_inline __must_check unsigned long
 raw_copy_to_user(void __user *dst, const void *src, unsigned long size)
 {
+	dst = mask_user_address(dst);
 	return copy_user_generic((__force void *)dst, src, size);
 }
 
-- 
2.47.0