[PATCH 3.15 12/37] s390/ptrace: fix PSW mask check

Greg Kroah-Hartman
2014-07-30T01:48:48Z

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

commit dab6cf55f81a6e16b8147aed9a843e1691dcd318 upstream.

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

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/kernel/ptrace.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -334,9 +334,14 @@ static int __poke_user(struct task_struc
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 tas

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;