From f0688c8b81d2ea239c3fb0b848f623b579238d99 Mon Sep 17 00:00:00 2001 From: Michal Nazarewicz Date: Tue, 17 Jun 2014 17:47:41 +0200 Subject: [PATCH] usb: gadget: f_fs: fix NULL pointer dereference when there are no strings MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If the descriptors do not need any strings and user space sends empty set of strings, the ffs->stringtabs field remains NULL. Thus *ffs->stringtabs in functionfs_bind leads to a NULL pointer dereferenece. The bug was introduced by commit [fd7c9a007f: “use usb_string_ids_n()”]. While at it, remove double initialisation of lang local variable in that function. ffs->strings_count does not need to be checked in any way since in the above scenario it will remain zero and usb_string_ids_n() is a no-operation when colled with 0 argument. Cc: # v2.6.36+ Signed-off-by: Michal Nazarewicz Signed-off-by: Felipe Balbi --- drivers/usb/gadget/f_fs.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c index 74202d67f911..8598c27c7d43 100644 --- a/drivers/usb/gadget/f_fs.c +++ b/drivers/usb/gadget/f_fs.c @@ -1483,11 +1483,13 @@ static int functionfs_bind(struct ffs_data *ffs, struct usb_composite_dev *cdev) ffs->ep0req->context = ffs; lang = ffs->stringtabs; - for (lang = ffs->stringtabs; *lang; ++lang) { - struct usb_string *str = (*lang)->strings; - int id = first_id; - for (; str->s; ++id, ++str) - str->id = id; + if (lang) { + for (; *lang; ++lang) { + struct usb_string *str = (*lang)->strings; + int id = first_id; + for (; str->s; ++id, ++str) + str->id = id; + } } ffs->gadget = cdev->gadget; -- 2.20.1