| Message ID | 20250328161823.2240125-1-fisaksen@baylibre.com |
|---|---|
| State | New |
| Headers | show |
| Series | usb: gadget: f_fs: Invalidate io_data when USB request is dequeued or completed | expand |
On Fri, Mar 28, 2025 at 05:17:15PM +0100, Frode Isaksen wrote: > From: Frode Isaksen <frode@meta.com> > > Invalidate io_data by setting context to NULL when USB request is > dequeued or completed, and check for NULL io_data in epfile_io_complete(). > The invalidation of io_data in req->context is done when exiting > epfile_io(), since then io_data will become invalid as it is allocated > on the stack. > The epfile_io_complete() may be called after ffs_epfile_io() returns > in case the wait_for_completion_interruptible() is interrupted. > This fixes a use-after-free error with the following call stack: > > Unable to handle kernel paging request at virtual address ffffffc02f7bbcc0 > pc : ffs_epfile_io_complete+0x30/0x48 > lr : usb_gadget_giveback_request+0x30/0xf8 > Call trace: > ffs_epfile_io_complete+0x30/0x48 > usb_gadget_giveback_request+0x30/0xf8 > dwc3_remove_requests+0x264/0x2e8 > dwc3_gadget_pullup+0x1d0/0x250 > kretprobe_trampoline+0x0/0xc4 > usb_gadget_remove_driver+0x40/0xf4 > usb_gadget_unregister_driver+0xdc/0x178 > unregister_gadget_item+0x40/0x6c > ffs_closed+0xd4/0x10c > ffs_data_clear+0x2c/0xf0 > ffs_data_closed+0x178/0x1ec > ffs_ep0_release+0x24/0x38 > __fput+0xe8/0x27c > > Signed-off-by: Frode Isaksen <frode@meta.com> > --- > This bug was discovered, tested and fixed (no more crashes seen) on Meta Quest 3 device. > Also tested on T.I. AM62x board. What commit id does this fix? Should it go to stable? > > drivers/usb/gadget/function/f_fs.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c > index 2dea9e42a0f8..f1be0a5c0bd0 100644 > --- a/drivers/usb/gadget/function/f_fs.c > +++ b/drivers/usb/gadget/function/f_fs.c > @@ -738,6 +738,9 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req) > { > struct ffs_io_data *io_data = req->context; > > + if (WARN_ON(io_data == NULL)) > + return; If this happens you just crashed the box (remember about panic-on-warn, which is still set in a few billion Linux systems these days...) Just handle the issue properly, no need to dump the stack and crash a device. But, what keeps io_data from changing after you have checked it? Where is the lock here? thanks, greg k-h
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 2dea9e42a0f8..f1be0a5c0bd0 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -738,6 +738,9 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req) { struct ffs_io_data *io_data = req->context; + if (WARN_ON(io_data == NULL)) + return; + if (req->status) io_data->status = req->status; else @@ -1126,6 +1129,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) spin_lock_irq(&epfile->ffs->eps_lock); if (epfile->ep != ep) { ret = -ESHUTDOWN; + req->context = NULL; goto error_lock; } /* @@ -1140,6 +1144,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) interrupted = io_data->status < 0; } + req->context = NULL; if (interrupted) ret = -EINTR; else if (io_data->read && io_data->status > 0)