s390/ptrace: fix PSW mask check

commit dab6cf55f81a6e16b8147aed9a843e1691dcd318 upstream.

The PSW mask check of the PTRACE_POKEUSR_AREA command is incorrect.
For the default user_mode=home address space layout the psw_user_bits
variable has the home space address-space-control bits set. But the
PSW_MASK_USER contains PSW_MASK_ASC, the ptrace validity check for the
PSW mask will therefore always fail.

Fixes CVE-2014-3534

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index afe82bc..b76230b 100644 (file)
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -292,7 +292,9 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
                 * psw and gprs are stored on the stack
                 */
                if (addr == (addr_t) &dummy->regs.psw.mask &&
-                   ((data & ~PSW_MASK_USER) != psw_user_bits ||
+                   (((data^psw_user_bits) & ~PSW_MASK_USER) ||
+                    (((data^psw_user_bits) & PSW_MASK_ASC) &&
+                     ((data|psw_user_bits) & PSW_MASK_ASC) == PSW_MASK_ASC) ||
                     ((data & PSW_MASK_EA) && !(data & PSW_MASK_BA))))
                        /* Invalid psw mask. */
                        return -EINVAL;
@@ -595,7 +597,10 @@ static int __poke_user_compat(struct task_struct *child,
                 */
                if (addr == (addr_t) &dummy32->regs.psw.mask) {
                        /* Build a 64 bit psw mask from 31 bit mask. */
-                       if ((tmp & ~PSW32_MASK_USER) != psw32_user_bits)
+                       if (((tmp^psw32_user_bits) & ~PSW32_MASK_USER) ||
+                           (((tmp^psw32_user_bits) & PSW32_MASK_ASC) &&
+                            ((tmp|psw32_user_bits) & PSW32_MASK_ASC)
+                            == PSW32_MASK_ASC))
                                /* Invalid psw mask. */
                                return -EINVAL;
                        regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |