__ptrace_may_access() should not deny sub-threads
authorMark Grondona <mgrondona@llnl.gov>
Wed, 11 Sep 2013 21:24:31 +0000 (14:24 -0700)
committerBen Hutchings <ben@decadent.org.uk>
Thu, 6 Aug 2015 23:32:18 +0000 (00:32 +0100)
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

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: Ben Hutchings <ben@decadent.org.uk>
Cc: Sheng Yong <shengyong1@huawei.com>

index 464b1fe..f07c144 100644 (file)
@@ -225,7 +225,7 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
        int dumpable = 0;
        /* Don't let security modules deny introspection */
-       if (task == current)
+       if (same_thread_group(task, current))
                return 0;
        tcred = __task_cred(task);