Commit 42db4123 authored by Alexey Gladkov (Intel)'s avatar Alexey Gladkov (Intel) Committed by Wen Zhiwei
Browse files

x86/tdx: Fix "in-kernel MMIO" check 

stable inclusion
from stable-v6.6.54
commit 4c0c5dcb5471de5fc8f0a1c4980e5815339e1cee
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAZ3K2

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c0c5dcb5471de5fc8f0a1c4980e5815339e1cee



--------------------------------

commit d4fc4d01471528da8a9797a065982e05090e1d81 upstream.

TDX only supports kernel-initiated MMIO operations. The handle_mmio()
function checks if the #VE exception occurred in the kernel and rejects
the operation if it did not.

However, userspace can deceive the kernel into performing MMIO on its
behalf. For example, if userspace can point a syscall to an MMIO address,
syscall does get_user() or put_user() on it, triggering MMIO #VE. The
kernel will treat the #VE as in-kernel MMIO.

Ensure that the target MMIO address is within the kernel before decoding
instruction.

Fixes: 31d58c4e ("x86/tdx: Handle in-kernel MMIO")
Signed-off-by: default avatarAlexey Gladkov (Intel) <legion@kernel.org>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc:stable@vger.kernel.org
Link: https://lore.kernel.org/all/565a804b80387970460a4ebc67c88d1380f61ad1.1726237595.git.legion%40kernel.org


Signed-off-by: default avatarAlexey Gladkov (Intel) <legion@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 9381dd97

arch/x86/coco/tdx/tdx.c

+6 −0
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <asm/insn.h>

#include <asm/insn-eval.h>

#include <asm/pgtable.h>

#include <asm/traps.h>



/* MMIO direction */

#define EPT_READ	0
@@ -405,6 +406,11 @@ static int handle_mmio(struct pt_regs *regs, struct ve_info *ve) 
			return -EINVAL;

	}



	if (!fault_in_kernel_space(ve->gla)) {

		WARN_ONCE(1, "Access to userspace address is not supported");

		return -EINVAL;

	}



	/*

	 * Reject EPT violation #VEs that split pages.

	 *