From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dan Carpenter , Andrzej Pietrasiewicz , Felipe Balbi Subject: [PATCH 3.19 085/177] usb: gadget: configfs: dont NUL-terminate (sub)compatible ids Date: Mon, 16 Mar 2015 15:08:12 +0100 Message-Id: <20150316140816.968163374@linuxfoundation.org> In-Reply-To: <20150316140813.085032723@linuxfoundation.org> References: <20150316140813.085032723@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrzej Pietrasiewicz commit a0456399fb07155637a2b597b91cc1c63bc25141 upstream. The "Extended Compat ID OS Feature Descriptor Specification" does not require the (sub)compatible ids to be NUL-terminated, because they are placed in a fixed-size buffer and only unused parts of it should contain NULs. If the buffer is fully utilized, there is no place for NULs. Consequently, the code which uses desc->ext_compat_id never expects the data contained to be NUL terminated. If the compatible id is stored after sub-compatible id, and the compatible id is full length (8 bytes), the (useless) NUL terminator overwrites the first byte of the sub-compatible id. If the sub-compatible id is full length (8 bytes), the (useless) NUL terminator ends up out of the buffer. The situation can happen in the RNDIS function, where the buffer is a part of struct f_rndis_opts. The next member of struct f_rndis_opts is a mutex, so its first byte gets overwritten. The said byte is a part of a mutex'es member which contains the information on whether the muext is locked or not. This can lead to a deadlock, because, in a configfs-composed gadget when a function is linked into a configuration with config_usb_cfg_link(), usb_get_function() is called, which then calls rndis_alloc(), which tries locking the same mutex and (wrongly) finds it already locked. This patch eliminates NUL terminating of the (sub)compatible id. Fixes: da4243145fb1: "usb: gadget: configfs: OS Extended Compatibility descriptors support" Reported-by: Dan Carpenter Signed-off-by: Andrzej Pietrasiewicz Signed-off-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/configfs.c | 2 -- 1 file changed, 2 deletions(-) --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -1161,7 +1161,6 @@ static ssize_t interf_grp_compatible_id_ if (desc->opts_mutex) mutex_lock(desc->opts_mutex); memcpy(desc->ext_compat_id, page, l); - desc->ext_compat_id[l] = '\0'; if (desc->opts_mutex) mutex_unlock(desc->opts_mutex); @@ -1192,7 +1191,6 @@ static ssize_t interf_grp_sub_compatible if (desc->opts_mutex) mutex_lock(desc->opts_mutex); memcpy(desc->ext_compat_id + 8, page, l); - desc->ext_compat_id[l + 8] = '\0'; if (desc->opts_mutex) mutex_unlock(desc->opts_mutex);