From e0129ef91ed758c06b6557c36124acfb2e1c7305 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 26 May 2010 14:42:53 -0700
Subject: [PATCH] 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>
---
kernel/ptrace.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4b4f72084d1b..74a3d693c196 100644
--- 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;
--
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