kexec: fix Oops in crash_shrink_memory()

[firefly-linux-kernel-4.4.55.git] / kernel / ptrace.c

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4b4f72084d1ba21b79ef01a41f0c50439840a6dc..74a3d693c196810f9eed784a2825ea50a7f9db83 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -596,18 +596,24 @@ int ptrace_request(struct task_struct *child, long request,
 
 #ifdef CONFIG_BINFMT_ELF_FDPIC
        case PTRACE_GETFDPIC: {
+               struct mm_struct *mm = get_task_mm(child);
                unsigned long tmp = 0;
 
+               ret = -ESRCH;
+               if (!mm)
+                       break;
+
                switch (addr) {
                case PTRACE_GETFDPIC_EXEC:
-                       tmp = child->mm->context.exec_fdpic_loadmap;
+                       tmp = mm->context.exec_fdpic_loadmap;
                        break;
                case PTRACE_GETFDPIC_INTERP:
-                       tmp = child->mm->context.interp_fdpic_loadmap;
+                       tmp = mm->context.interp_fdpic_loadmap;
                        break;
                default:
                        break;
                }
+               mmput(mm);
 
                ret = put_user(tmp, (unsigned long __user *) data);
                break;