[PATCH 3.12 001/104] s390/ptrace: fix PSW mask check

[Jiri Slaby]

From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 arch/s390/kernel/ptrace.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 9556905bd3ce..d4c5e6ba8410 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -322,7 +322,9 @@ 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;
@@ -655,7 +657,10 @@ 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) |
-- 
2.0.4

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