KVM: arm64: Unregister HYP sections from kmemleak in protected mode

commit 47e6223 upstream.

Booting a KVM host in protected mode with kmemleak quickly results
in a pretty bad crash, as kmemleak doesn't know that the HYP sections
have been taken away. This is specially true for the BSS section,
which is part of the kernel BSS section and registered at boot time
by kmemleak itself.

Unregister the HYP part of the BSS before making that section
HYP-private. The rest of the HYP-specific data is obtained via
the page allocator or lives in other sections, none of which is
subjected to kmemleak.

Fixes: 90134ac ("KVM: arm64: Protect the .hyp sections from the host")
Reviewed-by: Quentin Perret <qperret@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org # 5.13
Link: https://lore.kernel.org/r/20210802123830.2195174-3-maz@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/arm64/kvm/arm.c

@@ -15,6 +15,7 @@
 #include <linux/fs.h>
 #include <linux/mman.h>
 #include <linux/sched.h>
+#include <linux/kmemleak.h>
 #include <linux/kvm.h>
 #include <linux/kvm_irqfd.h>
 #include <linux/irqbypass.h>
@@ -1986,6 +1987,12 @@ static int finalize_hyp_mode(void)
 	if (ret)
 		return ret;
 
+	/*
+	 * Exclude HYP BSS from kmemleak so that it doesn't get peeked
+	 * at, which would end badly once the section is inaccessible.
+	 * None of other sections should ever be introspected.
+	 */
+	kmemleak_free_part(__hyp_bss_start, __hyp_bss_end - __hyp_bss_start);
 	ret = pkvm_mark_hyp_section(__hyp_bss);
 	if (ret)
 		return ret;