x86/signal: Fix restart_syscall number for x32 tasks

commit 22eab1108781eff09961ae7001704f7bd8fb1dce upstream.

When restarting a syscall with regs->ax == -ERESTART_RESTARTBLOCK,
regs->ax is assigned to a restart_syscall number.  For x32 tasks, this
syscall number must have __X32_SYSCALL_BIT set, otherwise it will be
an x86_64 syscall number instead of a valid x32 syscall number. This
issue has been there since the introduction of x32.

Reported-by: strace/tests/restart_syscall.test
Reported-and-tested-by: Elvira Khabirova <lineprinter0@gmail.com>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Cc: Elvira Khabirova <lineprinter0@gmail.com>
Link: http://lkml.kernel.org/r/20151130215436.GA25996@altlinux.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Zefan Li <lizefan@huawei.com>

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 115eac431483cbc6acc3a01d54f26abcd69d0227..b2952cac860f358bc914d296c1ecf6ba88567da7 100644 (file)
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -748,12 +748,15 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
        return 0;
 }
 
-#ifdef CONFIG_X86_32
-#define NR_restart_syscall     __NR_restart_syscall
-#else /* !CONFIG_X86_32 */
-#define NR_restart_syscall     \
-       test_thread_flag(TIF_IA32) ? __NR_ia32_restart_syscall : __NR_restart_syscall
-#endif /* CONFIG_X86_32 */
+static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
+{
+#if defined(CONFIG_X86_32) || !defined(CONFIG_X86_64)
+       return __NR_restart_syscall;
+#else /* !CONFIG_X86_32 && CONFIG_X86_64 */
+       return test_thread_flag(TIF_IA32) ? __NR_ia32_restart_syscall :
+               __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
+#endif /* CONFIG_X86_32 || !CONFIG_X86_64 */
+}
 
 /*
  * Note that 'init' is a special process: it doesn't get signals it doesn't
@@ -795,7 +798,7 @@ static void do_signal(struct pt_regs *regs)
                        break;
 
                case -ERESTART_RESTARTBLOCK:
-                       regs->ax = NR_restart_syscall;
+                       regs->ax = get_nr_restart_syscall(regs);
                        regs->ip -= 2;
                        break;
                }