Description: buffer over write in vgacon_scrollback_update
References:
 https://www.openwall.com/lists/oss-security/2020/07/28/2
 https://lists.openwall.net/linux-kernel/2020/07/29/234
Notes:
 carnil> Issue is only exploitable when CONFIG_VGACON_SOFT_SCROLLBACK is
 carnil> set which is not the case in Debian kernel config. So it is
 carnil> enough to handle tracking of fixes accordingly when upstream
 carnil> applies them.
 carnil> Source-wise fixed in 5.7.15 as well.
Bugs:
upstream: released (5.9-rc1) [ebfdfeeae8c01fcb2b3b74ffaf03876e20835d2d]
4.19-upstream-stable: released (4.19.139) [61219546f3036d2b4a1898be7a38da22e97a3b62]
4.9-upstream-stable: released (4.9.233) [8c19b606e78a2b08e1ea69eebd5c290913c89612]
sid: released (5.7.17-1)
4.19-buster-security: released (4.19.146-1)
4.9-stretch-security: released (4.9.240-1)