ARM: 5793/1: ARM: Check put_user fail in do_signal when enable OABI_COMPAT

Using OABI, the call to put_user in do_signal can fail causing the
calling app to hang.

The solution is to check if put_user fails and force the app to
seg fault in that case.

Tested with multiple sleeping apps/threads (using the nanosleep syscall)
and suspend/resume.

Signed-off-by: janboe <janboe.ye at gmail.com>
Signed-off-by: Jean Pihet <jpihet@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/signal.c

@@ -662,8 +662,12 @@ static void do_signal(struct pt_regs *regs, int syscall)
 				regs->ARM_sp -= 4;
 				usp = (u32 __user *)regs->ARM_sp;
 
-				put_user(regs->ARM_pc, usp);
-				regs->ARM_pc = KERN_RESTART_CODE;
+				if (put_user(regs->ARM_pc, usp) == 0) {
+					regs->ARM_pc = KERN_RESTART_CODE;
+				} else {
+					regs->ARM_sp += 4;
+					force_sigsegv(0, current);
+				}
 #endif
 			}
 		}