usb/io_edgeport: Fix a possible sleep-in-atomic bug in edge_bulk_in_callback

usb/io_edgeport: Fix a possible sleep-in-atomic bug in edge_bulk_in_callback

[Jia-Ju Bai]

According to drivers/usb/serial/io_edgeport.c, the driver may sleep 
under a spinlock.
The function call path is:
edge_bulk_in_callback (acquire the spinlock)
   process_rcvd_data
     process_rcvd_status
       change_port_settings
         send_iosp_ext_cmd
           write_cmd_usb
             usb_kill_urb --> may sleep

To fix it, usb_kill_urb() is removed from the error path after usb_submit_urb() fails.

This possible bug is found by my static analysis tool (DSAC) and checked by my code review.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 drivers/usb/serial/io_edgeport.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 219265c..17283f4 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -2282,7 +2282,6 @@ static int write_cmd_usb(struct edgeport_port *edge_port,
 		/* something went wrong */
 		dev_err(dev, "%s - usb_submit_urb(write command) failed, status = %d\n",
 			__func__, status);
-		usb_kill_urb(urb);
 		usb_free_urb(urb);
 		atomic_dec(&CmdUrbs);
 		return status;

usb/io_edgeport: Fix a possible sleep-in-atomic bug in edge_bulk_in_callback

[Johan Hovold]

On Wed, Dec 13, 2017 at 08:34:36PM +0800, Jia-Ju Bai wrote:
> According to drivers/usb/serial/io_edgeport.c, the driver may sleep 
> under a spinlock.
> The function call path is:
> edge_bulk_in_callback (acquire the spinlock)
>    process_rcvd_data
>      process_rcvd_status
>        change_port_settings
>          send_iosp_ext_cmd
>            write_cmd_usb
>              usb_kill_urb --> may sleep
> 
> To fix it, usb_kill_urb() is removed from the error path after usb_submit_urb() fails.

I added a "the redundant" before "usb_kill_urb()" in the above sentence
to make it more clear why this was done.

> This possible bug is found by my static analysis tool (DSAC) and checked by my code review.

And line-wrapped you commit message (at about 72 columns).

I also used a common prefix and shortened the summary to:

	USB: serial: io_edgeport: fix possible sleep-in-atomic

Just some minor nits, that you can keep in mind for your next patch
submission.

> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>

Thanks for reporting and fixing this. Now applied for -next.

Johan
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