linux-kernel - [PATCH] lkdtm: use SLAB_NO_MERGE instead of an empty constructor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20250318014533.1624852-1-harry.yoo@oracle.com>
Date: Tue, 18 Mar 2025 10:45:33 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Kees Cook <kees@...nel.org>
Cc: linux-kernel@...r.kernel.org, Harry Yoo <harry.yoo@...cle.com>
Subject: [PATCH] lkdtm: use SLAB_NO_MERGE instead of an empty constructor

Use SLAB_NO_MERGE flag to prevent merging instead of providing an
empty constructor. Using an empty constructor in this manner is an abuse
of slab interface.

The SLAB_NO_MERGE flag should be used with caution, but in this case,
it is acceptable as the cache is intended soley for debugging purposes.

No functional changes intended.

Signed-off-by: Harry Yoo <harry.yoo@...cle.com>
---
 drivers/misc/lkdtm/heap.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index b1b316f99703..c1a05b935894 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -355,23 +355,12 @@ static void lkdtm_SLAB_FREE_PAGE(void)
 	free_page(p);
 }
 
-/*
- * We have constructors to keep the caches distinctly separated without
- * needing to boot with "slab_nomerge".
- */
-static void ctor_double_free(void *region)
-{ }
-static void ctor_a(void *region)
-{ }
-static void ctor_b(void *region)
-{ }
-
 void __init lkdtm_heap_init(void)
 {
 	double_free_cache = kmem_cache_create("lkdtm-heap-double_free",
-					      64, 0, 0, ctor_double_free);
-	a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, 0, ctor_a);
-	b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, 0, ctor_b);
+					      64, 0, SLAB_NO_MERGE, NULL);
+	a_cache = kmem_cache_create("lkdtm-heap-a", 64, 0, SLAB_NO_MERGE, NULL);
+	b_cache = kmem_cache_create("lkdtm-heap-b", 64, 0, SLAB_NO_MERGE, NULL);
 }
 
 void __exit lkdtm_heap_exit(void)
-- 
2.43.0