usb: storage: suspicious code

From	"Gustavo A. R. Silva" <garsilva@embeddedor.com>
Newsgroups	linux.kernel
Subject	usb: storage: suspicious code
Date	2017-02-15 06:10 +0100
Message-ID	<tb00N-3Ky-1@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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Hello,

I ran into the following piece of code at drivers/usb/storage/jumpshot.c:305 (linux-next), and it seems a little bit suspicious:

// read the result.  apparently the bulk write can complete
// before the jumpshot drive is finished writing.  so we loop
// here until we get a good return code
waitcount = 0;
do {
	result = jumpshot_get_status(us);
	if (result != USB_STOR_TRANSPORT_GOOD) {
        	// I have not experimented to find the smallest value.
		//
		msleep(50);
	}
	} while ((result != USB_STOR_TRANSPORT_GOOD) && (waitcount < 10));

	if (result != USB_STOR_TRANSPORT_GOOD)
        	usb_stor_dbg(us, "Gah!  Waitcount = 10.  Bad write!?\n");

Variable 'waitcount' is never updated inside the do-while loop. So, either it isn't needed at all or line 316 should be modified (++waitcount < 10)

In case 'waitcount' isn't needed, lines 318 and 319 should be removed.

Can someone help me to clarify this so I can write a patch to fix this code?

Thank you
--
Gustavo A. R. Silva

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usb: storage: suspicious code "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-02-15 06:10 +0100
  Re: [usb-storage] usb: storage: suspicious code Oliver Neukum <oneukum@suse.com> - 2017-02-15 08:10 +0100
    Re: [usb-storage] usb: storage: suspicious code "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-02-15 08:50 +0100
      [PATCH] usb: storage: add missing pre-increment to variable "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-02-15 09:10 +0100
        Re: [usb-storage] [PATCH] usb: storage: add missing pre-increment  to variable Alan Stern <stern@rowland.harvard.edu> - 2017-02-15 16:30 +0100
          Re: [usb-storage] [PATCH] usb: storage: add missing pre-increment  to variable "Gustavo A. R. Silva" <garsilva@embeddedor.com> - 2017-02-21 00:40 +0100

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