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From:   Andrey Konovalov <andreyknvl@google.com>
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        Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH v9 13/20] kasan, mm: perform untagged pointers comparison in krealloc
Date:   Fri, 21 Sep 2018 17:13:35 +0200
Message-Id: <77d6321d5117c8b8e2267a707b693a6eb67ea17c.1537542735.git.andreyknvl@google.com>
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The krealloc function checks where the same buffer was reused or a new one
allocated by comparing kernel pointers. Tag-based KASAN changes memory tag
on the krealloc'ed chunk of memory and therefore also changes the pointer
tag of the returned pointer. Therefore we need to perform comparison on
untagged (with tags reset) pointers to check whether it's the same memory
region or not.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/slab_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 3abfa0f86118..221c1be3f45f 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1513,7 +1513,7 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags)
 	}
 
 	ret = __do_krealloc(p, new_size, flags);
-	if (ret && p != ret)
+	if (ret && kasan_reset_tag(p) != kasan_reset_tag(ret))
 		kfree(p);
 
 	return ret;
-- 
2.19.0.444.g18242da7ef-goog