On 6/1/2022 12:15 PM, Linyu Yuan wrote:
In ffs_epfile_io(), when read/write data in blocking mode, it will wait
the completion in interruptible mode, if task receive a signal, it will
terminate the wait, at same time, if function unbind occurs,
ffs_func_unbind() will kfree all eps, ffs_epfile_io() still try to
dequeue request by dereferencing ep which may become invalid.
Fix it by add ep spinlock and will not dereference ep if it is not valid.
Reported-by: Michael Wu <michael@xxxxxxxxxxxxxxxxx>
Reviewed-by: John Keeping <john@xxxxxxxxxxxx>
Signed-off-by: Linyu Yuan <quic_linyyuan@xxxxxxxxxxx>
---
v2: add Reviewed-by from John keeping
v3: add Reported-by from Michael Wu
drivers/usb/gadget/function/f_fs.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index d4d8940..9bf9287 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1077,6 +1077,11 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
spin_unlock_irq(&epfile->ffs->eps_lock);
if (wait_for_completion_interruptible(&io_data->done)) {
+ spin_lock_irq(&epfile->ffs->eps_lock);
+ if (epfile->ep != ep) {
+ ret = -ESHUTDOWN;
+ goto error_lock;
+ }
/*
* To avoid race condition with ffs_epfile_io_complete,
* dequeue the request first then check
@@ -1084,6 +1089,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
* condition with req->complete callback.
*/
usb_ep_dequeue(ep->ep, req);
+ spin_unlock_irq(&epfile->ffs->eps_lock);
wait_for_completion(&io_data->done);
interrupted = io_data->status < 0;
}
Tested-by: Michael Wu <michael@xxxxxxxxxxxxxxxxx>
I've tested Linyu's patches [PATCH v3 1/2] [PATCH v3 2/2]. I believe it
fixes the bug I reported.
What's more, John's solution [1] also works in my tests. It looks
simpler. I'm not sure if it's as complete as Linyu's solution.
[1] https://lore.kernel.org/linux-usb/YpUJkxWBNuZiW7Xk@donbot/
--
Regards,
Michael Wu
