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Message-Id: <20180209133935.882457967@linuxfoundation.org>
Date: Fri, 9 Feb 2018 14:39:33 +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,
Linus Torvalds <torvalds@...ux-foundation.org>,
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>
Subject: [PATCH 4.9 64/92] x86/syscall: Sanitize syscall table de-references under speculation
4.9-stable review patch. If anyone has any objections, please let me know.
------------------
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>
---
arch/x86/entry/common.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- 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>
@@ -277,7 +278,8 @@ __visible void do_syscall_64(struct pt_r
* regs->orig_ax, which changes the behavior of some syscalls.
*/
if (likely((nr & __SYSCALL_MASK) < NR_syscalls)) {
- regs->ax = sys_call_table[nr & __SYSCALL_MASK](
+ nr = array_index_nospec(nr & __SYSCALL_MASK, NR_syscalls);
+ regs->ax = sys_call_table[nr](
regs->di, regs->si, regs->dx,
regs->r10, regs->r8, regs->r9);
}
@@ -313,6 +315,7 @@ static __always_inline void do_syscall_3
}
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
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