+ __ptrace_may_access-should-not-deny-sub-threads.patch added to -mm tree

+ __ptrace_may_access-should-not-deny-sub-threads.patch added to -mm tree

[akpm]

Subject: + __ptrace_may_access-should-not-deny-sub-threads.patch added to -mm tree
To: mgrondona@llnl.gov,oleg@redhat.com,woodard@redhat.com
From: akpm@linux-foundation.org
Date: Wed, 14 Aug 2013 15:29:19 -0700


The patch titled
     Subject: __ptrace_may_access() should not deny sub-threads
has been added to the -mm tree.  Its filename is
     __ptrace_may_access-should-not-deny-sub-threads.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/__ptrace_may_access-should-not-deny-sub-threads.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/__ptrace_may_access-should-not-deny-sub-threads.patch

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------------------------------------------------------
From: Mark Grondona <mgrondona@llnl.gov>
Subject: __ptrace_may_access() should not deny sub-threads

__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>
---

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

diff -puN kernel/ptrace.c~__ptrace_may_access-should-not-deny-sub-threads kernel/ptrace.c
--- a/kernel/ptrace.c~__ptrace_may_access-should-not-deny-sub-threads
+++ a/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 -mm which might be from mgrondona@llnl.gov are

__ptrace_may_access-should-not-deny-sub-threads.patch