diff options
authorDan Williams <dan.j.williams@intel.com>2018-01-29 17:02:59 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-07 11:14:11 -0800
commitfecca4925b899956667078cff79790ada198851e (patch)
parent31d4cf78bb3d829f8c6347fa91db44bf8239c104 (diff)
x86/syscall: Sanitize syscall table de-references under speculation
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@linux-foundation.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arch@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Andy Lutomirski <luto@kernel.org> Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 99081340d19a..21dbdf0e476b 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -21,6 +21,7 @@
#include <linux/export.h>
#include <linux/context_tracking.h>
#include <linux/user-return-notifier.h>
+#include <linux/nospec.h>
#include <linux/uprobes.h>
#include <linux/livepatch.h>
#include <linux/syscalls.h>
@@ -282,7 +283,8 @@ __visible void do_syscall_64(struct pt_regs *regs)
* 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);
@@ -318,6 +320,7 @@ static __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