Re: [PATCH v1] usb: host: Fix possible kernel crash

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On Tuesday 10 July 2012 08:39 PM, Alan Stern wrote:
On Tue, 10 Jul 2012, Venu Byravarasu wrote:

Thanks Alan for your comments.

On Monday 09 July 2012 08:04 PM, Alan Stern wrote:
On Mon, 9 Jul 2012, Venu Byravarasu wrote:

In functions itd_complete &  sitd_complete, a pointer
by name stream may get dereferenced after freeing it, when
iso_stream_put is called with stream->refcount = 2.
I don't understand the problem.  Did you actually see this happen or is
it only theoretical?
Yes it is a theoretical problem, as complained by Coverity.
As per the logic you explained above, this change is not needed.
However coverity was complaining as below:

/kernel/drivers/usb/host/ehci-sched.c 1777 USE_AFTER_FREE Dereferencing
freed pointer "stream"

Hence to pacify coverity, this change is done.
Please let me know if you see any other better way to handle it.
This seems to be a false positive from Coverity.

In any case, I'm about to submit some patches which get rid of the
reference counting entirely.  So let's not worry about this.

Alan Stern

Thanks Alan for taking care of it, in your future patch.




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