The patch titled
Subject: mm/slab: add naive detection of double free
has been added to the -mm tree. Its filename is
slab-add-naive-detection-of-double-free.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slab-add-naive-detection-of-double-free.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slab-add-naive-detection-of-double-free.patch
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------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: mm/slab: add naive detection of double free
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
Link: http://lkml.kernel.org/r/20200625215548.389774-3-keescook@xxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Alexander Popov <alex.popov@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Cc: Matthew Garrett <mjg59@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Vijayanand Jitta <vjitta@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
--- a/mm/slab.c~slab-add-naive-detection-of-double-free
+++ a/mm/slab.c
@@ -749,6 +749,16 @@ static void drain_alien_cache(struct kme
}
}
+/* &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 kme
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 {
@@ -3466,7 +3476,7 @@ void ___cache_free(struct kmem_cache *ca
}
}
- ac->entry[ac->avail++] = objp;
+ __free_one(ac, objp);
}
/**
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
mm-expand-config_slab_freelist_hardened-to-include-slab.patch
slab-add-naive-detection-of-double-free.patch
exec-change-uselib2-is_sreg-failure-to-eacces.patch
exec-move-s_isreg-check-earlier.patch
exec-move-path_noexec-check-earlier.patch
