4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Dan Williams <dan.j.willi...@intel.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 <torva...@linux-foundation.org> Signed-off-by: Dan Williams <dan.j.willi...@intel.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Cc: linux-a...@vger.kernel.org Cc: kernel-harden...@lists.openwall.com Cc: gre...@linuxfoundation.org Cc: Andy Lutomirski <l...@kernel.org> Cc: a...@linux.intel.com Link: https://lkml.kernel.org/r/151727417984.33451.1216731042505722161.st...@dwillia2-desk3.amr.corp.intel.com Signed-off-by: David Woodhouse <d...@amazon.co.uk> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.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
