From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757927AbbGGOkA (ORCPT ); Tue, 7 Jul 2015 10:40:00 -0400 Received: from mx1.polytechnique.org ([129.104.30.34]:58888 "EHLO mx1.polytechnique.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757896AbbGGOjc (ORCPT ); Tue, 7 Jul 2015 10:39:32 -0400 From: Nicolas Iooss To: Greg Kroah-Hartman , Felipe Balbi , Joel Becker , Andrew Morton Cc: linux-kernel@vger.kernel.org Subject: [PATCH 2/2] configfs: fix kernel infoleak through user-controlled format string Date: Tue, 7 Jul 2015 22:28:00 +0800 Message-Id: <1436279280-28492-2-git-send-email-nicolas.iooss_linux@m4x.org> X-Mailer: git-send-email 2.4.5 In-Reply-To: <1436279280-28492-1-git-send-email-nicolas.iooss_linux@m4x.org> References: <1436279280-28492-1-git-send-email-nicolas.iooss_linux@m4x.org> X-AV-Checked: ClamAV using ClamSMTP at svoboda.polytechnique.org (Tue Jul 7 16:30:12 2015 +0200 (CEST)) X-Spam-Flag: No, tests=bogofilter, spamicity=0.000000, queueID=DA7351409B027 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some modules call config_item_init_type_name() and config_group_init_type_name() with parameter "name" directly controlled by userspace. These two functions call config_item_set_name() with this name used as a format string, which can be used to leak information such as content of the stack to userspace. For example, make_netconsole_target() in netconsole module calls config_item_init_type_name() with the name of a newly-created directory. This means that the following commands give some unexpected output, with configfs mounted in /sys/kernel/config/ and on a system with a configured eth0 ethernet interface: # modprobe netconsole # mkdir /sys/kernel/config/netconsole/target_%lx # echo eth0 > /sys/kernel/config/netconsole/target_%lx/dev_name # echo 1 > /sys/kernel/config/netconsole/target_%lx/enabled # echo eth0 > /sys/kernel/config/netconsole/target_%lx/dev_name # dmesg |tail -n1 [ 142.697668] netconsole: target (target_ffffffffc0ae8080) is enabled, disable to update parameters The directory name is correct but %lx has been interpreted in the internal item name, displayed here in the error message used by store_dev_name() in drivers/net/netconsole.c. To fix this, update every caller of config_item_set_name to use "%s" when operating on untrusted input. This issue was found using -Wformat-security gcc flag, once a __printf attribute has been added to config_item_set_name(). Signed-off-by: Nicolas Iooss --- drivers/usb/gadget/configfs.c | 2 +- fs/configfs/item.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c index 0495c94a23d7..289e20119fea 100644 --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -571,7 +571,7 @@ static struct config_group *function_make( if (IS_ERR(fi)) return ERR_CAST(fi); - ret = config_item_set_name(&fi->group.cg_item, name); + ret = config_item_set_name(&fi->group.cg_item, "%s", name); if (ret) { usb_put_function_instance(fi); return ERR_PTR(ret); diff --git a/fs/configfs/item.c b/fs/configfs/item.c index 4d6a30e76168..b863a09cd2f1 100644 --- a/fs/configfs/item.c +++ b/fs/configfs/item.c @@ -115,7 +115,7 @@ void config_item_init_type_name(struct config_item *item, const char *name, struct config_item_type *type) { - config_item_set_name(item, name); + config_item_set_name(item, "%s", name); item->ci_type = type; config_item_init(item); } @@ -124,7 +124,7 @@ EXPORT_SYMBOL(config_item_init_type_name); void config_group_init_type_name(struct config_group *group, const char *name, struct config_item_type *type) { - config_item_set_name(&group->cg_item, name); + config_item_set_name(&group->cg_item, "%s", name); group->cg_item.ci_type = type; config_group_init(group); } -- 2.4.5