In the Linux kernel, the following vulnerability has been resolved: x86/speculation: Fill RSB on vmexit for IBRS Prevent RSB underflow/poisoning attacks with RSB. While at it, add a bunch of comments to attempt to document the current state of tribal knowledge about RSB attacks and what exactly is being mitigated.
https://git.kernel.org/stable/c/f744b88dfc201bf8092833ec70b23c720188b527
https://git.kernel.org/stable/c/9756bba28470722dacb79ffce554336dd1f6a6cd
https://git.kernel.org/stable/c/8d5cff499a6d740c91ff37963907e0e983c37f0f
https://git.kernel.org/stable/c/8c38306e2e9257af4af2819aa287a4711ff36329
https://git.kernel.org/stable/c/4d7f72b6e1bc630bec7e4cd51814bc2b092bf153
https://git.kernel.org/stable/c/3d323b99ff5c8c57005184056d65f6af5b0479d8
https://git.kernel.org/stable/c/17a9fc4a7b91f8599223631bb6ae6416bc0de1c0