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usb: gadget: f_fs: fix NULL pointer dereference when there are no strings

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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: <stable@vger.kernel.org>  # v2.6.36+
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
Michal Nazarewicz 2014-06-17 17:47:41 +02:00 committed by Felipe Balbi
parent 82363cf2ee
commit f0688c8b81
1 changed files with 7 additions and 5 deletions
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12
drivers/usb/gadget/f_fs.c
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@ -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;