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2022-06-28T06:21:02.678556Z
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V 718
busdma: Protect ARM busdma bounce page counters using the bounce page lock.

In bus_dmamap_unload() on ARM, the counters for free_bpages and reserved_bpages
appear to be vulnerable to unprotected read-modify-write operations that result
in accounting that looks like a page leak.

This was noticed on a 2GB quad core i.MX6 system that has more than one device
attached via FTDI based USB serial connection.

Submitted by:	John Hein <jcfyecrayz@liamekaens.com>
Differential Revision:	https://reviews.freebsd.org/D35553
PR:		264836
Sponsored by:	NVIDIA Networking

(cherry picked from commit 6c4b6f55f77d8d7cee1b277bd6579a77d6890ef9)

Git Hash:   a0ffae30c593d829bc9cdd7b32017352e501d247
Git Author: hselasky@FreeBSD.org
END