From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Feng Tang <feng.tang@intel.com>, Ingo Molnar <mingo@redhat.com>,
"H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
rui.zhang@intel.com, andi.kleen@intel.com, dave.hansen@intel.com,
len.brown@intel.com
Subject: [PATCH -v1.1] x86/msr: Block writes to certain MSRs unconditionally
Date: Sat, 10 Apr 2021 17:33:38 +0200 [thread overview]
Message-ID: <20210410153338.GD21691@zn.tnic> (raw)
In-Reply-To: <437BACC3-A1F7-4C65-80C7-98F6652A14E6@amacapital.net>
On Sat, Apr 10, 2021 at 07:51:58AM -0700, Andy Lutomirski wrote:
> Can you add STAR, CSTAR, LSTAR, SYSENTER*, SYSCALL*, and EFER please?
Sure.
---
From: Borislav Petkov <bp@suse.de>
Date: Sat, 10 Apr 2021 14:08:13 +0200
There are a bunch of MSRs which luserspace has no business poking
at, whatsoever. Add a ban list and put the TSC-related MSRs and the
ring0-entry and features control MSRs in there. Issue a big juicy splat
to catch offenders.
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/msr.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index ed8ac6bcbafb..2435a619cd9f 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -78,6 +78,21 @@ static ssize_t msr_read(struct file *file, char __user *buf,
return bytes ? bytes : err;
}
+static const u32 msr_ban_list[] = {
+ MSR_IA32_TSC,
+ MSR_TSC_AUX,
+ MSR_IA32_TSC_ADJUST,
+ MSR_IA32_TSC_DEADLINE,
+ MSR_EFER,
+ MSR_STAR,
+ MSR_CSTAR,
+ MSR_LSTAR,
+ MSR_SYSCALL_MASK,
+ MSR_IA32_SYSENTER_CS,
+ MSR_IA32_SYSENTER_ESP,
+ MSR_IA32_SYSENTER_EIP,
+};
+
static int filter_write(u32 reg)
{
/*
@@ -89,6 +104,16 @@ static int filter_write(u32 reg)
* avoid saturating the ring buffer.
*/
static DEFINE_RATELIMIT_STATE(fw_rs, 30 * HZ, 1);
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(msr_ban_list); i++) {
+ if (msr_ban_list[i] != reg)
+ continue;
+
+ WARN_ONCE(1, "Blocked write to MSR 0x%x.\n", reg);
+
+ return -EINVAL;
+ }
switch (allow_writes) {
case MSR_WRITES_ON: return 0;
--
2.29.2
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-04-10 15:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-30 8:25 [RFC 1/2] x86/tsc: add a timer to make sure tsc_adjust is always checked Feng Tang
2021-03-30 8:25 ` [RFC 2/2] x86/tsc: mark tsc reliable for qualified platforms Feng Tang
2021-04-10 9:27 ` [RFC 1/2] x86/tsc: add a timer to make sure tsc_adjust is always checked Thomas Gleixner
2021-04-10 9:47 ` Borislav Petkov
2021-04-10 12:11 ` [PATCH] x86/msr: Block writes to certain MSRs unconditionally Borislav Petkov
2021-04-10 14:51 ` Andy Lutomirski
2021-04-10 15:33 ` Borislav Petkov [this message]
2021-04-10 18:52 ` Andi Kleen
2021-04-11 9:40 ` Borislav Petkov
2021-04-11 16:03 ` Andy Lutomirski
2021-04-11 16:43 ` Andi Kleen
2021-04-11 16:57 ` Andy Lutomirski
2021-04-11 17:03 ` Borislav Petkov
2021-04-11 23:21 ` Andy Lutomirski
2021-04-12 9:37 ` Borislav Petkov
2021-04-10 14:48 ` [RFC 1/2] x86/tsc: add a timer to make sure tsc_adjust is always checked Feng Tang
2021-04-10 15:38 ` Borislav Petkov
2021-04-10 18:43 ` Thomas Gleixner
2021-04-10 14:38 ` Feng Tang
2021-04-10 18:46 ` Thomas Gleixner
2021-04-11 7:21 ` Feng Tang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210410153338.GD21691@zn.tnic \
--to=bp@alien8.de \
--cc=andi.kleen@intel.com \
--cc=dave.hansen@intel.com \
--cc=feng.tang@intel.com \
--cc=hpa@zytor.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rui.zhang@intel.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).