Patch "__ptrace_may_access() should not deny sub-threads" has been added to the 3.10-stable tree

Patch "__ptrace_may_access() should not deny sub-threads" has been added to the 3.10-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    __ptrace_may_access() should not deny sub-threads

to the 3.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     __ptrace_may_access-should-not-deny-sub-threads.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 73af963f9f3036dffed55c3a2898598186db1045 Mon Sep 17 00:00:00 2001
From: Mark Grondona <mgrondona@llnl.gov>
Date: Wed, 11 Sep 2013 14:24:31 -0700
Subject: __ptrace_may_access() should not deny sub-threads

From: Mark Grondona <mgrondona@llnl.gov>

commit 73af963f9f3036dffed55c3a2898598186db1045 upstream.

__ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task !=
current, this can can lead to surprising results.

For example, a sub-thread can't readlink("/proc/self/exe") if the
executable is not readable.  setup_new_exec()->would_dump() notices that
inode_permission(MAY_READ) fails and then it does
set_dumpable(suid_dumpable).  After that get_dumpable() fails.

(It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we
could add PTRACE_MODE_NODUMPABLE)

Change __ptrace_may_access() to use same_thread_group() instead of "task
== current".  Any security check is pointless when the tasks share the
same ->mm.

Signed-off-by: Mark Grondona <mgrondona@llnl.gov>
Signed-off-by: Ben Woodard <woodard@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/ptrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -236,7 +236,7 @@ static int __ptrace_may_access(struct ta
 	 */
 	int dumpable = 0;
 	/* Don't let security modules deny introspection */
-	if (task == current)
+	if (same_thread_group(task, current))
 		return 0;
 	rcu_read_lock();
 	tcred = __task_cred(task);


Patches currently in stable-queue which might be from mgrondona@llnl.gov are

queue-3.10/__ptrace_may_access-should-not-deny-sub-threads.patch