From: Marco Elver <elver@google.com>
To: elver@google.com, akpm@linux-foundation.org
Cc: dvyukov@google.com, glider@google.com, andreyknvl@google.com,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, linux-mm@kvack.org
Subject: [PATCH] mm, kcsan: Instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS"
Date: Tue, 16 Jun 2020 14:56:17 +0200 [thread overview]
Message-ID: <20200616125617.237428-1-elver@google.com> (raw)
Provide the necessary KCSAN checks to assist with debugging racy
use-after-frees. While KASAN is more reliable at generally catching such
use-after-frees (due to its use of a quarantine), it can be difficult to
debug racy use-after-frees. If a reliable reproducer exists, KCSAN can
assist in debugging such issues.
Note: ASSERT_EXCLUSIVE_ACCESS is a convenience wrapper if the size is
simply sizeof(var). Instead, here we just use __kcsan_check_access()
explicitly to pass the correct size.
Signed-off-by: Marco Elver <elver@google.com>
---
mm/slab.c | 4 ++++
mm/slub.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/mm/slab.c b/mm/slab.c
index 9350062ffc1a..4c7013eeacd9 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3426,6 +3426,10 @@ static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
if (kasan_slab_free(cachep, objp, _RET_IP_))
return;
+ /* Use KCSAN to help debug racy use-after-free. */
+ __kcsan_check_access(objp, cachep->object_size,
+ KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT);
+
___cache_free(cachep, objp, caller);
}
diff --git a/mm/slub.c b/mm/slub.c
index b8f798b50d44..57db6ca2e0dc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1470,6 +1470,10 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x)
if (!(s->flags & SLAB_DEBUG_OBJECTS))
debug_check_no_obj_freed(x, s->object_size);
+ /* Use KCSAN to help debug racy use-after-free. */
+ __kcsan_check_access(x, s->object_size,
+ KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT);
+
/* KASAN might put x into memory quarantine, delaying its reuse */
return kasan_slab_free(s, x, _RET_IP_);
}
--
2.27.0.290.gba653c62da-goog
reply other threads:[~2020-06-16 12:56 UTC|newest]
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