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Message-Id: <1519382538-15143-16-git-send-email-jinpu.wangl@profitbricks.com>
Date: Fri, 23 Feb 2018 11:42:04 +0100
From: Jack Wang <jinpu.wang@...fitbricks.com>
To: gregkh@...uxfoundation.org,
stable@...r.kernel.org
Cc: Dan Williams <dan.j.williams@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-arch@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
Andy Lutomirski <luto@...nel.org>,
alan@...ux.intel.com,
David Woodhouse <dwmw@...zon.co.uk>,
Jack Wang <jinpu.wang@...fitbricks.com>
Subject: [stable 4.4 15/29] x86/syscall: Sanitize syscall table de-references under speculation
From: Dan Williams <dan.j.williams@...el.com>
(cherry picked from commit 2fbd7af5af8665d18bcefae3e9700be07e22b681)
The syscall table base is a user controlled function pointer in kernel
space. Use array_index_nospec() to prevent any out of bounds speculation.
While retpoline prevents speculating into a userspace directed target it
does not stop the pointer de-reference, the concern is leaking memory
relative to the syscall table base, by observing instruction cache
behavior.
Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-arch@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com
Cc: gregkh@...uxfoundation.org
Cc: Andy Lutomirski <luto@...nel.org>
Cc: alan@...ux.intel.com
Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[jwang: port to 4.4, no syscall_64]
Signed-off-by: Jack Wang <jinpu.wang@...fitbricks.com>
---
arch/x86/entry/common.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 1a4477c..b5eb1cc 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -20,6 +20,7 @@
#include <linux/export.h>
#include <linux/context_tracking.h>
#include <linux/user-return-notifier.h>
+#include <linux/nospec.h>
#include <linux/uprobes.h>
#include <asm/desc.h>
@@ -381,6 +382,7 @@ __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
}
if (likely(nr < IA32_NR_syscalls)) {
+ nr = array_index_nospec(nr, IA32_NR_syscalls);
/*
* It's possible that a 32-bit syscall implementation
* takes a 64-bit parameter but nonetheless assumes that
--
2.7.4
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