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: <sta...@vger.kernel.org> # v2.6.36+
Signed-off-by: Michal Nazarewicz <min...@mina86.com>
---
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 74202d6..8598c27 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;
--
2.0.0.526.g5318336
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