powerpc: Fix machine check problem on 32-bit kernels

This fixes a bug found by Dave Jones that means that it is possible
for userspace to provoke a machine check on 32-bit kernels.  This
also fixes a couple of other places where I found similar problems
by inspection.

Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 27f65b95184d..c2db642f4cdd 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -182,6 +182,8 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
         err |= __get_user(msr, &sc->gp_regs[PT_MSR]);
         if (err)
                 return err;
+        if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
+                return -EFAULT;
         /* Copy 33 vec registers (vr0..31 and vscr) from the stack */
         if (v_regs != 0 && (msr & MSR_VEC) != 0)
                 err |= __copy_from_user(current->thread.vr, v_regs,