From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751249AbdAQKAG (ORCPT ); Tue, 17 Jan 2017 05:00:06 -0500 Received: from hqemgate14.nvidia.com ([216.228.121.143]:8778 "EHLO hqemgate14.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbdAQKAE (ORCPT ); Tue, 17 Jan 2017 05:00:04 -0500 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 17 Jan 2017 01:59:37 -0800 From: Jim Lin To: CC: , , Jim Lin Subject: [PATCH v3] usb: gadget: configfs: Fix KASAN use-after-free Date: Tue, 17 Jan 2017 17:59:28 +0800 Message-ID: <1484647168-30135-1-git-send-email-jilin@nvidia.com> X-Mailer: git-send-email 2.7.4 X-NVConfidentiality: public MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When gadget is disconnected, running sequence is like this. . composite_disconnect . Call trace: usb_string_copy+0xd0/0x128 gadget_config_name_configuration_store+0x4 gadget_config_name_attr_store+0x40/0x50 configfs_write_file+0x198/0x1f4 vfs_write+0x100/0x220 SyS_write+0x58/0xa8 . configfs_composite_unbind . configfs_composite_bind In configfs_composite_bind, it has "cn->strings.s = cn->configuration;" When usb_string_copy is invoked. it would allocate memory, copy input string, release previous pointed memory space, and use new allocated memory. When gadget is connected, host sends down request to get information. Call trace: usb_gadget_get_string+0xec/0x168 lookup_string+0x64/0x98 composite_setup+0xa34/0x1ee8 If gadget is disconnected and connected quickly, in the failed case, cn->configuration memory has been released by usb_string_copy kfree but configfs_composite_bind hasn't been run in time to assign new allocated "cn->configuration" pointer to "cn->strings.s". When "strlen(s->s) of usb_gadget_get_string is being executed, the dangling memory is accessed, "BUG: KASAN: use-after-free" error occurs. Signed-off-by: Jim Lin --- Changes in v2: Changes in v3: Change commit description drivers/usb/gadget/configfs.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c index 78c4497..39fea62 100644 --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -106,6 +106,9 @@ struct gadget_config_name { struct list_head list; }; +#define MAX_USB_STRING_LEN 126 +#define MAX_USB_STRING_WITH_NULL_LEN (MAX_USB_STRING_LEN+1) + static int usb_string_copy(const char *s, char **s_copy) { int ret; @@ -115,12 +118,16 @@ static int usb_string_copy(const char *s, char **s_copy) if (ret > 126) return -EOVERFLOW; - str = kstrdup(s, GFP_KERNEL); - if (!str) - return -ENOMEM; + if (copy) { + str = copy; + } else { + str = kmalloc(MAX_USB_STRING_WITH_NULL_LEN, GFP_KERNEL); + if (!str) + return -ENOMEM; + } + strcpy(str, s); if (str[ret - 1] == '\n') str[ret - 1] = '\0'; - kfree(copy); *s_copy = str; return 0; } -- 2.7.4