Commit 7612bfee authored Aug 15, 2012 by Kees Cook Committed by James Morris Aug 17, 2012

Yama: access task_struct->comm directly



The core ptrace access checking routine holds a task lock, and when
reporting a failure, Yama takes a separate task lock. To avoid a
potential deadlock with two ptracers taking the opposite locks, do not
use get_task_comm() and just use ->comm directly since accuracy is not
important for the report.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
CC: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

parent d9875690

security/yama/yama_lsm.c

+2 −8

Original line number	Diff line number	Diff line
		@@ -279,12 +279,9 @@ static int yama_ptrace_access_check(struct task_struct *child,
		}

		if (rc) {
		char name[sizeof(current->comm)];
		printk_ratelimited(KERN_NOTICE
		"ptrace of pid %d was attempted by: %s (pid %d)\n",
		child->pid,
		get_task_comm(name, current),
		current->pid);
		child->pid, current->comm, current->pid);
		}

		return rc;
		@@ -319,12 +316,9 @@ static int yama_ptrace_traceme(struct task_struct *parent)
		}

		if (rc) {
		char name[sizeof(current->comm)];
		printk_ratelimited(KERN_NOTICE
		"ptraceme of pid %d was attempted by: %s (pid %d)\n",
		current->pid,
		get_task_comm(name, parent),
		parent->pid);
		current->pid, parent->comm, parent->pid);
		}

		return rc;