From: Frode Isaksen frode@meta.com

Invalidate io_data by setting context to NULL when USB request is dequeued or interrupted, 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 Cc: stable@vger.kernel.org --- v1 -> v2: Removed WARN_ON() in ffs_epfile_io_complete(). Clarified commit message. Added stable Cc tag.

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..e35d32e7be58 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 (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)