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Date: Mon, 26 Aug 2019 14:53:42 +0200
From: Borislav Petkov <bp@...e.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Pu Wen <puwen@...on.cn>, Thomas Gleixner <tglx@...utronix.de>,
Tom Lendacky <thomas.lendacky@....com>,
Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [GIT pull] x86/urgent for 5.3-rc5
On Sun, Aug 25, 2019 at 10:17:23PM +0200, Borislav Petkov wrote:
> > I think WARN_ONCE() is good. It's big enough that it will show up in
> > dmesg if anybody looks, and if nobody looks I think distros still have
> > logging for things like that, don't they?
>
> Probably. Lemme research that.
So there's a whole bunch of daemons doing desktop notifications along with a
desktop notifications spec, yadda yadda:
https://wiki.archlinux.org/index.php/Desktop_notifications
but installing an openSUSE Leap 15.1 in a guest and that is a default
desktop installation doesn't give me any notifications. I installed
notification-daemon and whatnot but nada.
Which means, that we cannot guarantee that every user would see it.
There might be installations which miss it.
So the only thing I can think of right now is to make that single line
pr_emerg() so that it atleast spews into the terminals when suspending:
linux-6qfo:~ # echo "suspend" > /sys/power/disk
linux-6qfo:~ # echo "mem" > /sys/power/state
<--- resume guest.
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.416145] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.423091] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.427426] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.434699] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.442587] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.449047] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.456328] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.462198] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.470120] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.477302] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.484605] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.490115] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.497508] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.505350] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
Message from syslogd@...ux-6qfo at Aug 26 14:48:05 ...
kernel:[ 40.513336] RDRAND gives funky smelling output, might consider not using it by booting with "nordrand"
---
Assuming the user has at least a single terminal open. But someone might
have a better idea.
Current diff:
---
commit d46b23c4be1b4acae7d21c97be189131e200f6d0 (HEAD -> refs/heads/rc5+1-rdrand)
Author: Borislav Petkov <bp@...e.de>
Date: Sun Aug 25 22:50:18 2019 +0200
WIP
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
diff --git a/arch/x86/kernel/cpu/rdrand.c b/arch/x86/kernel/cpu/rdrand.c
index 5c900f9527ff..b02d1ce91081 100644
--- a/arch/x86/kernel/cpu/rdrand.c
+++ b/arch/x86/kernel/cpu/rdrand.c
@@ -29,7 +29,8 @@ __setup("nordrand", x86_rdrand_setup);
#ifdef CONFIG_ARCH_RANDOM
void x86_init_rdrand(struct cpuinfo_x86 *c)
{
- unsigned long tmp;
+ unsigned int changed = 0;
+ unsigned long tmp, prev;
int i;
if (!cpu_has(c, X86_FEATURE_RDRAND))
@@ -42,5 +43,27 @@ void x86_init_rdrand(struct cpuinfo_x86 *c)
return;
}
}
+
+ /*
+ * Stupid sanity-check whether RDRAND does *actually* generate
+ * some at least random-looking data.
+ */
+ prev = tmp;
+ for (i = 0; i < SANITY_CHECK_LOOPS; i++) {
+ if (rdrand_long(&tmp)) {
+ if (prev != tmp)
+ changed++;
+
+ prev = tmp;
+ }
+ }
+
+ if (!changed) {
+ pr_emerg(
+"RDRAND gives funky smelling output, might consider not using it by booting with \"nordrand\"");
+ WARN_ON_ONCE(1);
+ }
+
+
}
#endif
---
--
Regards/Gruss,
Boris.
SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 247165, AG München
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