mm/vmalloc.c: vmap(): don't allow invalid pages

mm/vmalloc.c: vmap(): don't allow invalid pages

vmap() takes struct page *pages as one of arguments, and user may provide
an invalid pointer which would lead to data abort at address translation
later.

Currently, kernel checks the pages against NULL.  In my case, however, the
address was not NULL, and was big enough so that the hardware generated
Address Size Abort on arm64.

Interestingly, this abort happens even if copy_from_kernel_nofault() is
used, which is quite inconvenient for debugging purposes.

This patch adds a pfn_valid() check into vmap() path, so that invalid
mapping will not be created.

Link: https://lkml.kernel.org/r/20220119012109.551931-1-yury.norov@gmail.com
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ding Tianhong <dingtianhong@huawei.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Alexey Klimov <aklimov@redhat.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>