Commit 83050a4e authored Feb 09, 2016 by Riley Andrews Committed by Greg Kroah-Hartman Feb 11, 2016

android: drivers: Avoid debugfs race in binder



If a /d/binder/proc/[pid] entry is kept open after linux has
torn down the associated process, binder_proc_show can deference
an invalid binder_proc that has been stashed in the debugfs
inode.  Validate that the binder_proc ptr passed into binder_proc_show
has not been freed by looking for it within the global process list
whilst the global lock is held. If the ptr is not valid, print nothing.

Cc: Colin Cross <ccross@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Dmitry Shmidt <dimitrysh@google.com>
Cc: Rom Lemarchand <romlem@google.com>
Cc: Serban Constantinescu <serban.constantinescu@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
[jstultz: Minor commit message tweaks]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 212265e5

drivers/android/binder.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -3600,13 +3600,24 @@ static int binder_transactions_show(struct seq_file m, void unused)

		static int binder_proc_show(struct seq_file m, void unused)
		{
		struct binder_proc *itr;
		struct binder_proc *proc = m->private;
		int do_lock = !binder_debug_no_lock;
		bool valid_proc = false;

		if (do_lock)
		binder_lock(__func__);

		hlist_for_each_entry(itr, &binder_procs, proc_node) {
		if (itr == proc) {
		valid_proc = true;
		break;
		}
		}
		if (valid_proc) {
		seq_puts(m, "binder proc state:\n");
		print_binder_proc(m, proc, 1);
		}
		if (do_lock)
		binder_unlock(__func__);
		return 0;