[PATCH v2] cred: prevent slab cache merging for cred_jar

[Mohammed EL Kadiri <med08elkadiri@gmail.com>]

Add SLAB_NO_MERGE to cred_jar to ensure struct cred objects get
dedicated slab pages, preventing the allocator from merging this
cache with other similarly-sized caches. This is a hardening measure
to provide type isolation for credential objects.

Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Mohammed EL Kadiri <med08elkadiri@gmail.com>
---

Changes in v2:
  - Collected Reviewed-by tag from Kees Cook.
  - No code changes from v1.

 kernel/cred.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index 9676965c0981..0e4ee60a5acd 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -557,7 +557,7 @@ void __init cred_init(void)
 {
 	/* allocate a slab in which we can store credentials */
 	cred_jar = KMEM_CACHE(cred,
-			      SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
+			      SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT | SLAB_NO_MERGE);
 }
 
 /**
-- 
2.43.0