ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm
Now that Mike Frysinger unified the FDPIC ptrace code, we can fix the
unsafe usage of child->mm in ptrace_request(PTRACE_GETFDPIC).
We have the reference to task_struct, and ptrace_check_attach() verified
the tracee is stopped. But nothing can protect from SIGKILL after that,
we must not assume child->mm != NULL.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Mike Frysinger <vapier.adi@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Greg Ungerer <gerg@snapgear.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4b4f720..74a3d69 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -596,18 +596,24 @@
#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;