Linux: irda: Fix lockdep annotations in hashbin_delete() (CVE-2017-6348)

[Salvatore Bonaccorso <carnil () debian org>]

Hi

CVE-2017-6348 was assigned by MITRE to the following (via
https://cveform.mitre.org/):

https://git.kernel.org/linus/4c03b862b12f980456f9de92db6d508a4999b788

> irda: Fix lockdep annotations in hashbin_delete().
>
> A nested lock depth was added to the hasbin_delete() code but it
> doesn't actually work some well and results in tons of lockdep splats.
>
> Fix the code instead to properly drop the lock around the operation
> and just keep peeking the head of the hashbin queue.

Quoting a note from Ben Hutchins: "This actually changes locking, not just
lockdep annotations. So I think it fixes a potential deadlock."

The fix was as well backported to 4.9.13.

Regards,
Salvatore