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From:   Ilya Leoshkevich <iii@linux.ibm.com>
To:     Alexander Gordeev <agordeev@linux.ibm.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Marco Elver <elver@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Pekka Enberg <penberg@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>
Cc:     Christian Borntraeger <borntraeger@linux.ibm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-s390@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org,
        Mark Rutland <mark.rutland@arm.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Sven Schnelle <svens@linux.ibm.com>,
        Ilya Leoshkevich <iii@linux.ibm.com>
Subject: [PATCH 13/32] kmsan: Support SLAB_POISON
Date:   Wed, 15 Nov 2023 21:30:45 +0100
Message-ID: <20231115203401.2495875-14-iii@linux.ibm.com>
In-Reply-To: <20231115203401.2495875-1-iii@linux.ibm.com>
References: <20231115203401.2495875-1-iii@linux.ibm.com>
MIME-Version: 1.0
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Avoid false KMSAN negatives with SLUB_DEBUG by allowing
kmsan_slab_free() to poison the freed memory, and by preventing
init_object() from unpoisoning new allocations.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 mm/kmsan/hooks.c | 2 +-
 mm/slub.c        | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 7b5814412e9f..7a30274b893c 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -76,7 +76,7 @@ void kmsan_slab_free(struct kmem_cache *s, void *object)
 		return;
 
 	/* RCU slabs could be legally used after free within the RCU period */
-	if (unlikely(s->flags & (SLAB_TYPESAFE_BY_RCU | SLAB_POISON)))
+	if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU))
 		return;
 	/*
 	 * If there's a constructor, freed memory must remain in the same state
diff --git a/mm/slub.c b/mm/slub.c
index 63d281dfacdb..8d9aa4d7cb7e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1024,7 +1024,8 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct slab *slab,
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 }
 
-static void init_object(struct kmem_cache *s, void *object, u8 val)
+__no_sanitize_memory static void
+init_object(struct kmem_cache *s, void *object, u8 val)
 {
 	u8 *p = kasan_reset_tag(object);
 	unsigned int poison_size = s->object_size;
-- 
2.41.0