efi_loader: Ensure memory allocations are page aligned

When the max_addr parameter of efi_find_free_memory() is within bounds
of an existing map and fits the reservation, we just return that address
as allocation value.

That breaks however if max_addr is not page aligned. So ensure that it
always comes to us page aligned, simplifying the allocation logic.

Without this, I've seen breakage where we were allocating pages at -1U
(32bit) which fits into a region that spans beyond 0x100000000. In that
case, we would return 0xffffffff as a valid memory allocation, although
we usually do guarantee they are all page aligned.

Fix this by aligning the max address argument always.

Signed-off-by: Alexander Graf <agraf@suse.de>

lib/efi_loader/efi_memory.c

@@ -294,6 +294,12 @@ static uint64_t efi_find_free_memory(uint64_t len, uint64_t max_addr)
 {
 	struct list_head *lhandle;
 
+	/*
+	 * Prealign input max address, so we simplify our matching
+	 * logic below and can just reuse it as return pointer.
+	 */
+	max_addr &= ~EFI_PAGE_MASK;
+
 	list_for_each(lhandle, &efi_mem) {
 		struct efi_mem_list *lmem = list_entry(lhandle,
 			struct efi_mem_list, link);