AZL-80627

In the Linux kernel, the following vulnerability has been resolved:

arm64: io: Extract user memory type in ioremap_prot()

The only caller of ioremapprot() outside of the generic ioremap() implementation is genericaccessphys(), which passes a 'pgprott' value determined from the user mapping of the target 'pfn' being accessed by the kernel. On arm64, the 'pgprott' contains all of the non-address bits from the pte, including the permission controls, and so we end up returning a new user mapping from ioremapprot() which faults when accessed from the kernel on systems with PAN:

| Unable to handle kernel read from unreadable memory at virtual address ffff80008ea89000 | ... | Call trace: | __memcpyfromio+0x80/0xf8 | genericaccess_phys+0x20c/0x2b8 | __accessremotevm+0x46c/0x5b8 | access_remotevm+0x18/0x30 | environread+0x238/0x3e8 | vfsread+0xe4/0x2b0 | ksysread+0xcc/0x178 | __arm64sysread+0x4c/0x68

Extract only the memory type from the user 'pgprott' in ioremapprot() and assert that we're being passed a user mapping, to protect us against any changes in future that may require additional handling. To avoid falsely flagging users of ioremap(), provide our own ioremap() macro which simply wraps _ioremapprot().