From: Arve Hjønnevåg <arve@android.com>
Date: Mon, 9 Apr 2007 10:13:02 +0000 (+0700)
Subject: [ARM] Add code to prevent system calls from being restarted muliple times before... 
X-Git-Tag: firefly_0821_release~9833^2~5^2~361
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=acf6f51ba7048e99a1f8b7d5cea70b2faf7774c7;p=firefly-linux-kernel-4.4.55.git

[ARM] Add code to prevent system calls from being restarted muliple times before returning from the kernel.

Fixes crashes with thumb syscalls.
---

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 907d5a620bca..15c46d27ca27 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -602,6 +602,14 @@ setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
 
 static inline void setup_syscall_restart(struct pt_regs *regs)
 {
+	if (regs->ARM_ORIG_r0 == -ERESTARTNOHAND ||
+	    regs->ARM_ORIG_r0 == -ERESTARTSYS ||
+	    regs->ARM_ORIG_r0 == -ERESTARTNOINTR ||
+	    regs->ARM_ORIG_r0 == -ERESTART_RESTARTBLOCK) {
+		/* the syscall cannot be safely restarted, return -EINTR instead */
+		regs->ARM_r0 = -EINTR;
+		return;
+	}
 	regs->ARM_r0 = regs->ARM_ORIG_r0;
 	regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
 }
@@ -734,6 +742,7 @@ static void do_signal(struct pt_regs *regs, int syscall)
 	 */
 	if (syscall) {
 		if (regs->ARM_r0 == -ERESTART_RESTARTBLOCK) {
+			regs->ARM_r0 = -EAGAIN; /* prevent multiple restarts */
 			if (thumb_mode(regs)) {
 				regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
 				regs->ARM_pc -= 2;