Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964900AbdCJMho (ORCPT ); Fri, 10 Mar 2017 07:37:44 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45145 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936628AbdCJMPv (ORCPT ); Fri, 10 Mar 2017 07:15:51 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Alan Stern" , "Felipe Balbi" , "Andrey Konovalov" Date: Fri, 10 Mar 2017 11:46:22 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 141/370] USB: gadgetfs: fix unbounded memory allocation bug In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3141 Lines: 66 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Alan Stern commit faab50984fe6636e616c7cc3d30308ba391d36fd upstream. Andrey Konovalov reports that fuzz testing with syzkaller causes a KASAN warning in gadgetfs: BUG: KASAN: slab-out-of-bounds in dev_config+0x86f/0x1190 at addr ffff88003c47e160 Write of size 65537 by task syz-executor0/6356 CPU: 3 PID: 6356 Comm: syz-executor0 Not tainted 4.9.0-rc7+ #19 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffff88003c107ad8 ffffffff81f96aba ffffffff3dc11ef0 1ffff10007820eee ffffed0007820ee6 ffff88003dc11f00 0000000041b58ab3 ffffffff8598b4c8 ffffffff81f96828 ffffffff813fb4a0 ffff88003b6eadc0 ffff88003c107738 Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [] dump_stack+0x292/0x398 lib/dump_stack.c:51 [] kasan_object_err+0x1c/0x70 mm/kasan/report.c:159 [< inline >] print_address_description mm/kasan/report.c:197 [] kasan_report_error+0x1f0/0x4e0 mm/kasan/report.c:286 [] kasan_report+0x35/0x40 mm/kasan/report.c:306 [< inline >] check_memory_region_inline mm/kasan/kasan.c:308 [] check_memory_region+0x139/0x190 mm/kasan/kasan.c:315 [] kasan_check_write+0x14/0x20 mm/kasan/kasan.c:326 [< inline >] copy_from_user arch/x86/include/asm/uaccess.h:689 [< inline >] ep0_write drivers/usb/gadget/legacy/inode.c:1135 [] dev_config+0x86f/0x1190 drivers/usb/gadget/legacy/inode.c:1759 [] __vfs_write+0x5d5/0x760 fs/read_write.c:510 [] vfs_write+0x170/0x4e0 fs/read_write.c:560 [< inline >] SYSC_write fs/read_write.c:607 [] SyS_write+0xfb/0x230 fs/read_write.c:599 [] entry_SYSCALL_64_fastpath+0x1f/0xc2 Indeed, there is a comment saying that the value of len is restricted to a 16-bit integer, but the code doesn't actually do this. This patch fixes the warning. It replaces the comment with a computation that forces the amount of data copied from the user in ep0_write() to be no larger than the wLength size for the control transfer, which is a 16-bit quantity. Signed-off-by: Alan Stern Reported-by: Andrey Konovalov Tested-by: Andrey Konovalov Signed-off-by: Felipe Balbi [bwh: Backported to 3.16: adjust filename] Signed-off-by: Ben Hutchings --- drivers/usb/gadget/inode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/usb/gadget/inode.c +++ b/drivers/usb/gadget/inode.c @@ -1200,7 +1200,7 @@ ep0_write (struct file *fd, const char _ /* data and/or status stage for control request */ } else if (dev->state == STATE_DEV_SETUP) { - /* IN DATA+STATUS caller makes len <= wLength */ + len = min_t(size_t, len, dev->setup_wLength); if (dev->setup_in) { retval = setup_req (dev->gadget->ep0, dev->req, len); if (retval == 0) {