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>

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 01e3c08..8fdeca2 100644 (file)
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -803,10 +803,13 @@ static int do_setcontext(struct ucontext __user *ucp, struct pt_regs *regs, int
                if (__get_user(cmcp, &ucp->uc_regs))
                        return -EFAULT;
                mcp = (struct mcontext __user *)(u64)cmcp;
+               /* no need to check access_ok(mcp), since mcp < 4GB */
        }
 #else
        if (__get_user(mcp, &ucp->uc_regs))
                return -EFAULT;
+       if (!access_ok(VERIFY_READ, mcp, sizeof(*mcp)))
+               return -EFAULT;
 #endif
        restore_sigmask(&set);
        if (restore_user_regs(regs, mcp, sig))
@@ -908,13 +911,14 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
 {
        struct sig_dbg_op op;
        int i;
+       unsigned char tmp;
        unsigned long new_msr = regs->msr;
 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
        unsigned long new_dbcr0 = current->thread.dbcr0;
 #endif
 
        for (i=0; i<ndbg; i++) {
-               if (__copy_from_user(&op, dbg, sizeof(op)))
+               if (copy_from_user(&op, dbg + i, sizeof(op)))
                        return -EFAULT;
                switch (op.dbg_type) {
                case SIG_DBG_SINGLE_STEPPING:
@@ -959,6 +963,11 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
        current->thread.dbcr0 = new_dbcr0;
 #endif
 
+       if (!access_ok(VERIFY_READ, ctx, sizeof(*ctx))
+           || __get_user(tmp, (u8 __user *) ctx)
+           || __get_user(tmp, (u8 __user *) (ctx + 1) - 1))
+               return -EFAULT;
+
        /*
         * If we get a fault copying the context into the kernel's
         * image of the user's registers, we can't just return -EFAULT

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 27f65b9..c2db642 100644 (file)
--- 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,