From 1bf72720281770162c87990697eae1ba2f1d917a Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 16 May 2019 09:09:35 +0200
Subject: [PATCH 1/2] cpu/speculation: Warn on unsupported mitigations=
parameter
Currently, if the user specifies an unsupported mitigation strategy on the
kernel command line, it will be ignored silently. The code will fall back
to the default strategy, possibly leaving the system more vulnerable than
expected.
This may happen due to e.g. a simple typo, or, for a stable kernel release,
because not all mitigation strategies have been backported.
Inform the user by printing a message.
Fixes: 98af8452945c5565 ("cpu/speculation: Add 'mitigations=' cmdline option")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190516070935.22546-1-geert@linux-m68k.org
---
kernel/cpu.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 077fde6fb953..551db494f153 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2339,6 +2339,9 @@ static int __init mitigations_parse_cmdline(char *arg)
cpu_mitigations = CPU_MITIGATIONS_AUTO;
else if (!strcmp(arg, "auto,nosmt"))
cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+ else
+ pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
+ arg);
return 0;
}
From 33d4a5a7a5b4d02915d765064b2319e90a11cbde Mon Sep 17 00:00:00 2001
From: Eiichi Tsukata <devel@etsukata.com>
Date: Thu, 27 Jun 2019 11:47:32 +0900
Subject: [PATCH 2/2] cpu/hotplug: Fix out-of-bounds read when setting fail
state
Setting invalid value to /sys/devices/system/cpu/cpuX/hotplug/fail
can control `struct cpuhp_step *sp` address, results in the following
global-out-of-bounds read.
Reproducer:
# echo -2 > /sys/devices/system/cpu/cpu0/hotplug/fail
KASAN report:
BUG: KASAN: global-out-of-bounds in write_cpuhp_fail+0x2cd/0x2e0
Read of size 8 at addr ffffffff89734438 by task bash/1941
CPU: 0 PID: 1941 Comm: bash Not tainted 5.2.0-rc6+ #31
Call Trace:
write_cpuhp_fail+0x2cd/0x2e0
dev_attr_store+0x58/0x80
sysfs_kf_write+0x13d/0x1a0
kernfs_fop_write+0x2bc/0x460
vfs_write+0x1e1/0x560
ksys_write+0x126/0x250
do_syscall_64+0xc1/0x390
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f05e4f4c970
The buggy address belongs to the variable:
cpu_hotplug_lock+0x98/0xa0
Memory state around the buggy address:
ffffffff89734300: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff89734380: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff89734400: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
^
ffffffff89734480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff89734500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Add a sanity check for the value written from user space.
Fixes: 1db49484f21ed ("smp/hotplug: Hotplug state fail injection")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/20190627024732.31672-1-devel@etsukata.com
---
kernel/cpu.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 551db494f153..ef1c565edc5d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1964,6 +1964,9 @@ static ssize_t write_cpuhp_fail(struct device *dev,
if (ret)
return ret;
+ if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
+ return -EINVAL;
+
/*
* Cannot fail STARTING/DYING callbacks.
*/