linux-kernel - [PATCH 5.11 069/775] x86/MSR: Filter MSR writes through X86_IOC_WRMSR

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Date:   Mon,  1 Mar 2021 17:03:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Misono Tomohiro <misono.tomohiro@...fujitsu.com>,
        Borislav Petkov <bp@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 069/775] x86/MSR: Filter MSR writes through X86_IOC_WRMSR_REGS ioctl too

From: Misono Tomohiro <misono.tomohiro@...fujitsu.com>

[ Upstream commit 02a16aa13574c8526beadfc9ae8cc9b66315fa2d ]

Commit

  a7e1f67ed29f ("x86/msr: Filter MSR writes")

introduced a module parameter to disable writing to the MSR device file
and tainted the kernel upon writing. As MSR registers can be written by
the X86_IOC_WRMSR_REGS ioctl too, the same filtering and tainting should
be applied to the ioctl as well.

 [ bp: Massage commit message and space out statements. ]

Fixes: a7e1f67ed29f ("x86/msr: Filter MSR writes")
Signed-off-by: Misono Tomohiro <misono.tomohiro@...fujitsu.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20210127122456.13939-1-misono.tomohiro@jp.fujitsu.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/msr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 8a67d1fa8dc58..ed8ac6bcbafb2 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -182,6 +182,13 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 		err = security_locked_down(LOCKDOWN_MSR);
 		if (err)
 			break;
+
+		err = filter_write(regs[1]);
+		if (err)
+			return err;
+
+		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+
 		err = wrmsr_safe_regs_on_cpu(cpu, regs);
 		if (err)
 			break;
-- 
2.27.0