From: Kees Cook <keescook@chromium.org>
To: akpm@linux-foundation.org
Cc: Kees Cook <keescook@chromium.org>,
Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
Christoph Lameter <cl@linux.com>,
Alexander Popov <alex.popov@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
vinmenon@codeaurora.org, Matthew Garrett <mjg59@google.com>,
Jann Horn <jannh@google.com>,
Vijayanand Jitta <vjitta@codeaurora.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] slab: Add naive detection of double free
Date: Thu, 25 Jun 2020 14:55:48 -0700 [thread overview]
Message-ID: <20200625215548.389774-3-keescook@chromium.org> (raw)
In-Reply-To: <20200625215548.389774-1-keescook@chromium.org>
Similar to commit ce6fa91b9363 ("mm/slub.c: add a naive detection
of double free or corruption"), add a very cheap double-free check
for SLAB under CONFIG_SLAB_FREELIST_HARDENED. With this added, the
"SLAB_FREE_DOUBLE" LKDTM test passes under SLAB:
lkdtm: Performing direct entry SLAB_FREE_DOUBLE
lkdtm: Attempting double slab free ...
------------[ cut here ]------------
WARNING: CPU: 2 PID: 2193 at mm/slab.c:757 ___cache _free+0x325/0x390
Signed-off-by: Kees Cook <keescook@chromium.org>
---
mm/slab.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index ebac5e400ad0..bbff6705ab2b 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -749,6 +749,16 @@ static void drain_alien_cache(struct kmem_cache *cachep,
}
}
+/* &alien->lock must be held by alien callers. */
+static __always_inline void __free_one(struct array_cache *ac, void *objp)
+{
+ /* Avoid trivial double-free. */
+ if (IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) &&
+ WARN_ON_ONCE(ac->avail > 0 && ac->entry[ac->avail - 1] == objp))
+ return;
+ ac->entry[ac->avail++] = objp;
+}
+
static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
int node, int page_node)
{
@@ -767,7 +777,7 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
STATS_INC_ACOVERFLOW(cachep);
__drain_alien_cache(cachep, ac, page_node, &list);
}
- ac->entry[ac->avail++] = objp;
+ __free_one(ac, objp);
spin_unlock(&alien->lock);
slabs_destroy(cachep, &list);
} else {
@@ -3457,7 +3467,7 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
}
}
- ac->entry[ac->avail++] = objp;
+ __free_one(ac, objp);
}
/**
--
2.25.1
next prev parent reply other threads:[~2020-06-25 21:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-25 21:55 [PATCH v2 0/2] mm: Expand CONFIG_SLAB_FREELIST_HARDENED to include SLAB Kees Cook
2020-06-25 21:55 ` [PATCH v2 1/2] " Kees Cook
2020-08-04 17:15 ` Vlastimil Babka
2020-06-25 21:55 ` Kees Cook [this message]
2020-08-04 17:18 ` [PATCH v2 2/2] slab: Add naive detection of double free Vlastimil Babka
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