target/xtensa: fix OOB TLB entry access

target/xtensa: fix OOB TLB entry access

r[id]tlb[01], [iw][id]tlb opcodes use TLB way index passed in a register
by the guest. The host uses 3 bits of the index for ITLB indexing and 4
bits for DTLB, but there's only 7 entries in the ITLB array and 10 in
the DTLB array, so a malicious guest may trigger out-of-bound access to
these arrays.

Change split_tlb_entry_spec return type to bool to indicate whether TLB
way passed to it is valid. Change get_tlb_entry to return NULL in case
invalid TLB way is requested. Add assertion to xtensa_tlb_get_entry that
requested TLB way and entry indices are valid. Add checks to the
[rwi]tlb helpers that requested TLB way is valid and return 0 or do
nothing when it's not.

Cc: qemu-stable@nongnu.org
Fixes: b67ea0cd7441 ("target-xtensa: implement memory protection options")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20231215120307.545381-1-jcmvbkbc@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>