s390/ptrace: fix PSW mask check

The PSW mask check of the PTRACE_POKEUSR_AREA command is incorrect.
The PSW_MASK_USER define contains the PSW_MASK_ASC bits, the ptrace
interface accepts all combinations for the address-space-control
bits. To protect the kernel space the PSW mask check in ptrace needs
to reject the address-space-control bit combination for home space.

Fixes CVE-2014-3534

Cc: stable@vger.kernel.org
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 2d716734b5b1..5dc7ad9e2fbf 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -334,9 +334,14 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
                         unsigned long mask = PSW_MASK_USER;
 
                         mask |= is_ri_task(child) ? PSW_MASK_RI : 0;
-                        if ((data & ~mask) != PSW_USER_BITS)
+                        if ((data ^ PSW_USER_BITS) & ~mask)
+                                /* Invalid psw mask. */
+                                return -EINVAL;
+                        if ((data & PSW_MASK_ASC) == PSW_ASC_HOME)
+                                /* Invalid address-space-control bits */
                                 return -EINVAL;
                         if ((data & PSW_MASK_EA) && !(data & PSW_MASK_BA))
+                                /* Invalid addressing mode bits */
                                 return -EINVAL;
                 }
                 *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr) = data;
@@ -672,9 +677,12 @@ static int __poke_user_compat(struct task_struct *child,
 
                         mask |= is_ri_task(child) ? PSW32_MASK_RI : 0;
                         /* Build a 64 bit psw mask from 31 bit mask. */
-                        if ((tmp & ~mask) != PSW32_USER_BITS)
+                        if ((tmp ^ PSW32_USER_BITS) & ~mask)
                                 /* Invalid psw mask. */
                                 return -EINVAL;
+                        if ((data & PSW32_MASK_ASC) == PSW32_ASC_HOME)
+                                /* Invalid address-space-control bits */
+                                return -EINVAL;
                         regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
                                 (regs->psw.mask & PSW_MASK_BA) |
                                 (__u64)(tmp & mask) << 32;