From e0129ef91ed758c06b6557c36124acfb2e1c7305 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov 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 Acked-by: Mike Frysinger Acked-by: David Howells Cc: Paul Mundt Cc: Greg Ungerer Acked-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/ptrace.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) 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 @@ 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; -- 2.7.4