Commit 26dca996 authored Jan 14, 2022 by Andrey Konovalov Committed by Linus Torvalds Jan 15, 2022

kasan: fix quarantine conflicting with init_on_free

KASAN's quarantine might save its metadata inside freed objects.  As
this happens after the memory is zeroed by the slab allocator when
init_on_free is enabled, the memory coming out of quarantine is not
properly zeroed.

This causes lib/test_meminit.c tests to fail with Generic KASAN.

Zero the metadata when the object is removed from quarantine.

Link: https://lkml.kernel.org/r/2805da5df4b57138fdacd671f5d227d58950ba54.1640037083.git.andreyknvl@google.com


Fixes: 6471384a ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f98f966c

mm/kasan/quarantine.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -132,11 +132,22 @@ static void qlink_to_object(struct qlist_node qlink, struct kmem_cache *cache)
		static void qlink_free(struct qlist_node qlink, struct kmem_cache cache)
		{
		void *object = qlink_to_object(qlink, cache);
		struct kasan_free_meta *meta = kasan_get_free_meta(cache, object);
		unsigned long flags;

		if (IS_ENABLED(CONFIG_SLAB))
		local_irq_save(flags);

		/*
		* If init_on_free is enabled and KASAN's free metadata is stored in
		* the object, zero the metadata. Otherwise, the object's memory will
		* not be properly zeroed, as KASAN saves the metadata after the slab
		* allocator zeroes the object.
		*/
		if (slab_want_init_on_free(cache) &&
		cache->kasan_info.free_meta_offset == 0)
		memzero_explicit(meta, sizeof(*meta));

		/*
		* As the object now gets freed from the quarantine, assume that its
		* free track is no longer valid.