Description: io_uring: ensure symmetry in handling iter types in loop_rw_iter()
References:
 https://www.openwall.com/lists/oss-security/2021/09/18/2
 https://twitter.com/chompie1337/status/1439743758447398918
 https://www.graplsecurity.com/post/iou-ring-exploiting-the-linux-kernel
 https://github.com/chompie1337/Linux_LPE_io_uring_CVE-2021-41073
Notes:
Bugs:
upstream: released (5.15-rc2) [16c8d2df7ec0eed31b7d3b61cb13206a7fb930cc]
5.10-upstream-stable: released (5.10.68) [ce8f81b76d3bef7b9fe6c8f84d029ab898b19469]
4.19-upstream-stable: N/A "Vulnerable code introduced later"
4.9-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (5.14.6-2) [bugfix/all/io_uring-ensure-symmetry-in-handling-iter-types-in-l.patch]
5.10-bullseye-security: released (5.10.46-5) [bugfix/all/io_uring-ensure-symmetry-in-handling-iter-types-in-l.patch]
4.19-buster-security: N/A "Vulnerable code introduced later"
4.9-stretch-security: N/A "Vulnerable code introduced later"