riscv: Sync efi page table's kernel mappings before switching

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: riscv: Sync efi page table's kernel mappings before switching The EFI page table is initially created as a copy of the kernel page table. With VMAP_STACK enabled, kernel stacks are allocated in the vmalloc area: if the stack is allocated in a new PGD (one that was not present at the moment of the efi page table creation or not synced in a previous vmalloc fault), the kernel will take a trap when switching to the efi page table when the vmalloc kernel stack is accessed, resulting in a kernel panic. Fix that by updating the efi kernel mappings before switching to the efi page table.

References

• https://git.kernel.org/stable/c/fa7a7d185ef380546b4b1fed6f84f31dbae8cec7
• https://git.kernel.org/stable/c/96f479383d92944406d4b3f2bc03c2f640def9f1
• https://git.kernel.org/stable/c/3f105a742725a1b78766a55169f1d827732e62b8