+ mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch added to -mm tree

* + mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch added to -mm tree
@ 2020-06-16 18:14 akpm
  0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2020-06-16 18:14 UTC (permalink / raw)
  To: mm-commits, rientjes, penberg, iamjoonsoo.kim, glider, cl,
	andreyknvl, elver


The patch titled
     Subject: mm, kcsan: instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS"
has been added to the -mm tree.  Its filename is
     mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch

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------------------------------------------------------
From: Marco Elver <elver@google.com>
Subject: mm, kcsan: instrument SLAB/SLUB free with "ASSERT_EXCLUSIVE_ACCESS"

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.

Link: http://lkml.kernel.org/r/20200616125617.237428-1-elver@google.com
Signed-off-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slab.c |    4 ++++
 mm/slub.c |    4 ++++
 2 files changed, 8 insertions(+)

--- a/mm/slab.c~mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access
+++ a/mm/slab.c
@@ -3426,6 +3426,10 @@ static __always_inline void __cache_free
 	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);
 }
 
--- a/mm/slub.c~mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access
+++ a/mm/slub.c
@@ -1470,6 +1470,10 @@ static __always_inline bool slab_free_ho
 	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_);
 }
_

Patches currently in -mm which might be from elver@google.com are

mm-kcsan-instrument-slab-slub-free-with-assert_exclusive_access.patch

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