From 83050a4e21979fe1821916fce2fca36255569ed3 Mon Sep 17 00:00:00 2001 From: Riley Andrews Date: Tue, 9 Feb 2016 21:05:33 -0800 Subject: [PATCH] android: drivers: Avoid debugfs race in binder MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Arve Hjønnevåg Cc: Dmitry Shmidt Cc: Rom Lemarchand Cc: Serban Constantinescu Cc: Greg Kroah-Hartman Cc: Android Kernel Team Signed-off-by: Dmitry Shmidt [jstultz: Minor commit message tweaks] Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 1db376184955..f0ce9959d14d 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -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__); - seq_puts(m, "binder proc state:\n"); - print_binder_proc(m, proc, 1); + + 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;