From f0f42204d0cc04a63ac61fdaa3b6a269ea0dc08b Mon Sep 17 00:00:00 2001 From: Andrzej Pietrasiewicz Date: Mon, 20 Jan 2014 08:33:50 +0100 Subject: [PATCH] usb: gadget: fix NULL pointer dereference Fix possible NULL pointer dereference introduced in commit 219580e (usb: f_fs: check quirk to pad epout buf size when not aligned to maxpacketsize) In cases we do wait with: wait_event_interruptible(epfile->wait, (ep = epfile->ep)); for endpoint to be enabled, functionfs_bind() has not been called yet and epfile->ffs->gadget is still NULL and the automatic variable 'gadget' has been initialized with NULL at the point of its definition. Later on it is used as a parameter to: usb_ep_align_maybe(gadget, ep->ep, len) which in turn dereferences it. This patch fixes it by moving the actual assignment to the local 'gadget' variable after the potential waiting has completed. Signed-off-by: Andrzej Pietrasiewicz Acked-by: Michal Nazarewicz Signed-off-by: Felipe Balbi --- drivers/usb/gadget/f_fs.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c index 306a2b5..2b43343 100644 --- a/drivers/usb/gadget/f_fs.c +++ b/drivers/usb/gadget/f_fs.c @@ -585,7 +585,6 @@ static ssize_t ffs_epfile_io(struct file *file, char __user *buf, size_t len, int read) { struct ffs_epfile *epfile = file->private_data; - struct usb_gadget *gadget = epfile->ffs->gadget; struct ffs_ep *ep; char *data = NULL; ssize_t ret, data_len; @@ -622,6 +621,12 @@ static ssize_t ffs_epfile_io(struct file *file, /* Allocate & copy */ if (!halt) { /* + * if we _do_ wait above, the epfile->ffs->gadget might be NULL + * before the waiting completes, so do not assign to 'gadget' earlier + */ + struct usb_gadget *gadget = epfile->ffs->gadget; + + /* * Controller may require buffer size to be aligned to * maxpacketsize of an out endpoint. */ -- 2.7.4