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. Cc: <stable@xxxxxxxxxxxxxxx> # v3.16+ Fixes: da4243145fb1: "usb: gadget: configfs: OS Extended Compatibility descriptors support" Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx> --- drivers/usb/gadget/configfs.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c index 7564814..c42765b3a0 100644 --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -1161,7 +1161,6 @@ static ssize_t interf_grp_compatible_id_store(struct usb_os_desc *desc, 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_id_store(struct usb_os_desc *desc, 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); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
