arm64: vdso: don't free unallocated pages

The aarch32_vdso_pages[] array never has entries allocated in the C_VVAR
or C_VDSO slots, and as the array is zero initialized these contain
NULL.

However in __aarch32_alloc_vdso_pages() when
aarch32_alloc_kuser_vdso_page() fails we attempt to free the page whose
struct page is at NULL, which is obviously nonsensical.

This patch removes the erroneous page freeing.

Fixes: 7c1deeeb01 ("arm64: compat: VDSO setup for compat layer")
Cc: <stable@vger.kernel.org> # 5.3.x-
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/vdso.c

@@ -260,18 +260,7 @@ static int __aarch32_alloc_vdso_pages(void)
 	if (ret)
 		return ret;
 
-	ret = aarch32_alloc_kuser_vdso_page();
-	if (ret) {
-		unsigned long c_vvar =
-			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VVAR]);
-		unsigned long c_vdso =
-			(unsigned long)page_to_virt(aarch32_vdso_pages[C_VDSO]);
-
-		free_page(c_vvar);
-		free_page(c_vdso);
-	}
-
-	return ret;
+	return aarch32_alloc_kuser_vdso_page();
 }
 #else
 static int __aarch32_alloc_vdso_pages(void)