riscv: uprobes: Add missing fence.i after building the XOL buffer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: riscv: uprobes: Add missing fence.i after building the XOL buffer The XOL (execute out-of-line) buffer is used to single-step the replaced instruction(s) for uprobes. The RISC-V port was missing a proper fence.i (i$ flushing) after constructing the XOL buffer, which can result in incorrect execution of stale/broken instructions. This was found running the BPF selftests "test_progs: uprobe_autoattach, attach_probe" on the Spacemit K1/X60, where the uprobes tests randomly blew up.

References

• https://git.kernel.org/stable/c/be6d98766ac952d38241d5a5b213f363afa421c3
• https://git.kernel.org/stable/c/b6d8d4d01ca8514fa89b05355f296758a91e2297
• https://git.kernel.org/stable/c/77c956152a3a7c7a18b68f3654f70565b2181d03
• https://git.kernel.org/stable/c/bcf6d3158c5902d92b6d62335af4422b7bf7c4e2
• https://git.kernel.org/stable/c/1dbb95a36499374c51b47ee8ae258a8862c20978
• https://git.kernel.org/stable/c/7d1d19a11cfbfd8bae1d89cc010b2cc397cd0c48