keys: prevent slab cache merging for key_jar

Started by Mohammed EL Kadiri on Jun 10, 2026 · 2 messages from 2 authors · Last reply Jun 10, 2026

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STALE150d LANDED · 1 review, 1 by a maintainer

Status: Landed in mainline as 0934c38b12bd on 2026-06-15.

1 review trailer.

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Mohammed EL Kadiri Jun 10, 06:50 #

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Add SLAB_NO_MERGE to key_jar to prevent the allocator from merging it
with other similarly-sized caches. This hardens struct key isolation by
ensuring dedicated slab pages.

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Mohammed EL Kadiri <redacted>
---
 security/keys/key.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/keys/key.c b/security/keys/key.c
index 3bbdde778631..592b65cf8539 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c

@@ -1275,7 +1275,7 @@ void __init key_init(void)
 {
 	/* allocate a slab in which we can store keys */
 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
-			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_NO_MERGE, NULL);
 
 	/* add the special key types */
 	list_add_tail(&key_type_keyring.link, &key_types_list);

-- 
2.43.0

Jarkko Sakkinen replied to Mohammed EL Kadiri Jun 10, 09:57 #

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On Wed, Jun 10, 2026 at 07:50:52AM +0100, Mohammed EL Kadiri wrote:

quoted hunk

Add SLAB_NO_MERGE to key_jar to prevent the allocator from merging it
with other similarly-sized caches. This hardens struct key isolation by
ensuring dedicated slab pages.

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Mohammed EL Kadiri <redacted>
---
 security/keys/key.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/keys/key.c b/security/keys/key.c
index 3bbdde778631..592b65cf8539 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c

@@ -1275,7 +1275,7 @@ void __init key_init(void)
 {
 	/* allocate a slab in which we can store keys */
 	key_jar = kmem_cache_create("key_jar", sizeof(struct key),
-			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_NO_MERGE, NULL);
 
 	/* add the special key types */
 	list_add_tail(&key_type_keyring.link, &key_types_list);

-- 
2.43.0

I swapped the commit.

https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/log/?h=for-next-keys

BR, Jarkko

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