[PATCH] check put_user fail in do_signal when enable OABI_COMPACT

[Janboe Ye]

Using OABI, do_signal need to copy restart_syscall to user stack.
It is possible that put_user fail. This triggers flush_icache page
fault and crash kernel.

Signed-off-by: janboe <janboe.ye at gmail.com>
---
 arch/arm/kernel/signal.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index f6bc5d4..2122d43 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -626,6 +626,7 @@ static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
 	struct k_sigaction ka;
 	siginfo_t info;
 	int signr;
+	int ret = 0;
 
 	/*
 	 * We want the common case to go fast, which
@@ -679,16 +680,20 @@ static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
 				 */
 				swival = swival - __NR_SYSCALL_BASE + __NR_OABI_SYSCALL_BASE;
 
-				put_user(regs->ARM_pc, &usp[0]);
+				ret |= put_user(regs->ARM_pc, &usp[0]);
 				/* swi __NR_restart_syscall */
-				put_user(0xef000000 | swival, &usp[1]);
+				ret |= put_user(0xef000000 | swival, &usp[1]);
 				/* ldr	pc, [sp], #12 */
-				put_user(0xe49df00c, &usp[2]);
-
-				flush_icache_range((unsigned long)usp,
-						   (unsigned long)(usp + 3));
-
-				regs->ARM_pc = regs->ARM_sp + 4;
+				ret |= put_user(0xe49df00c, &usp[2]);
+				if (!ret) {
+					flush_icache_range((unsigned long)usp,
+						(unsigned long)(usp + 3));
+
+					regs->ARM_pc = regs->ARM_sp + 4;
+				} else {
+					regs->ARM_sp += 12;
+					force_sigsegv(0, current);
+				}
 #endif
 			}
 		}
-- 
1.6.3.3