x86: compat_sys_ptrace

This adds a generic definition of compat_sys_ptrace that calls
compat_arch_ptrace, parallel to sys_ptrace/arch_ptrace.  Some
machines needing this already define a function by that name.
The new generic function is defined only on machines that
put #define __ARCH_WANT_COMPAT_SYS_PTRACE into asm/ptrace.h.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 53 insertions, 0 deletions

diff --git a/include/linux/compat.h b/include/linux/compat.h
index a907fbede6c3..d38655f2be70 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -247,6 +247,13 @@ extern int compat_ptrace_request(struct task_struct *child,
                                  compat_long_t request,
                                  compat_ulong_t addr, compat_ulong_t data);
 
+#ifdef __ARCH_WANT_COMPAT_SYS_PTRACE
+extern long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
+                               compat_ulong_t addr, compat_ulong_t data);
+asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
+                                  compat_long_t addr, compat_long_t data);
+#endif  /* __ARCH_WANT_COMPAT_SYS_PTRACE */
+
 /*
  * epoll (fs/eventpoll.c) compat bits follow ...
  */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index ed1c3d56c2cd..e6e9b8be4b05 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -644,4 +644,50 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 
         return ret;
 }
+
+#ifdef __ARCH_WANT_COMPAT_SYS_PTRACE
+asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
+                                  compat_long_t addr, compat_long_t data)
+{
+        struct task_struct *child;
+        long ret;
+
+        /*
+         * This lock_kernel fixes a subtle race with suid exec
+         */
+        lock_kernel();
+        if (request == PTRACE_TRACEME) {
+                ret = ptrace_traceme();
+                goto out;
+        }
+
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                goto out;
+        }
+
+        if (request == PTRACE_ATTACH) {
+                ret = ptrace_attach(child);
+                /*
+                 * Some architectures need to do book-keeping after
+                 * a ptrace attach.
+                 */
+                if (!ret)
+                        arch_ptrace_attach(child);
+                goto out_put_task_struct;
+        }
+
+        ret = ptrace_check_attach(child, request == PTRACE_KILL);
+        if (!ret)
+                ret = compat_arch_ptrace(child, request, addr, data);
+
+ out_put_task_struct:
+        put_task_struct(child);
+ out:
+        unlock_kernel();
+        return ret;
+}
+#endif /* __ARCH_WANT_COMPAT_SYS_PTRACE */
+
 #endif  /* CONFIG_COMPAT */