Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756790AbcJ3PoP (ORCPT ); Sun, 30 Oct 2016 11:44:15 -0400 Received: from thejh.net ([37.221.195.125]:53998 "EHLO thejh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753429AbcJ3PoO (ORCPT ); Sun, 30 Oct 2016 11:44:14 -0400 From: Jann Horn To: Arnd Bergmann , Greg Kroah-Hartman , Sudip Mukherjee Cc: linux-kernel@vger.kernel.org, linux-parport@lists.infradead.org, Andy Lutomirski Subject: [PATCH] ppdev: fix double-free of pp->pdev->name Date: Sun, 30 Oct 2016 16:44:08 +0100 Message-Id: <1477842248-2234-1-git-send-email-jann@thejh.net> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1677 Lines: 48 free_pardevice() is called by parport_unregister_device() and already frees pp->pdev->name, don't try to do it again. This bug causes kernel crashes. I found and verified this with KASAN and some added pr_emerg()s: [ 60.316568] pp_release: pp->pdev->name == ffff88039cb264c0 [ 60.316692] free_pardevice: freeing par_dev->name at ffff88039cb264c0 [ 60.316706] pp_release: kfree(ffff88039cb264c0) [ 60.316714] ========================================================== [ 60.316722] BUG: Double free or freeing an invalid pointer [ 60.316731] Unexpected shadow byte: 0xFB [ 60.316801] Object at ffff88039cb264c0, in cache kmalloc-32 size: 32 [ 60.316813] Allocated: [ 60.316824] PID = 1695 [ 60.316869] Freed: [ 60.316880] PID = 1695 [ 60.316935] ========================================================== CCing Andy Lutomirski because I think this is what broke vmapped stacks for me - after applying this patch, vmapped stacks worked for me. Previously, I got oopses (and lockups) caused by area->pages[0] being 0x400000000 in __vunmap(), with area->pages being allocated in the kmalloc area. Signed-off-by: Jann Horn --- drivers/char/ppdev.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c index d23368874710..6af1ce04b3da 100644 --- a/drivers/char/ppdev.c +++ b/drivers/char/ppdev.c @@ -748,10 +748,7 @@ static int pp_release(struct inode *inode, struct file *file) } if (pp->pdev) { - const char *name = pp->pdev->name; - parport_unregister_device(pp->pdev); - kfree(name); pp->pdev = NULL; pr_debug(CHRDEV "%x: unregistered pardevice\n", minor); } -- 2.1.4