Description: XSA-374: xen-netback: take a reference to the RX task thread
References:
 https://xenbits.xen.org/xsa/advisory-374.html
Notes:
 carnil> Commit fixes 2ac061ce97f4 ('xen/netback: cleanup init and
 carnil> deinit code') in 5.5-rc1.
Bugs:
upstream: released (5.13-rc6) [107866a8eb0b664675a260f1ba0655010fac1e08]
5.10-upstream-stable: released (5.10.43) [6b53db8c4c14b4e7256f058d202908b54a7b85b4]
4.19-upstream-stable: N/A "Vulnerable code introduced later"
4.9-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.10.46-1)
4.19-buster-security: N/A "Vulnerable code introduced later"
4.9-stretch-security: N/A "Vulnerable code introduced later"