From c8961332d6da59b8a39998f46831fe7871cd1519 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 23 Feb 2018 11:42:04 +0100 Subject: x86/syscall: Sanitize syscall table de-references under speculation (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 Signed-off-by: Dan Williams Signed-off-by: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: kernel-hardening@lists.openwall.com Cc: gregkh@linuxfoundation.org Cc: Andy Lutomirski Cc: alan@linux.intel.com Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: David Woodhouse [jwang: port to 4.4, no syscall_64] Signed-off-by: Jack Wang Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/common.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/entry/common.c') diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 1a4477cedc49..b5eb1cca70a0 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include @@ -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 -- cgit v1.2.3