From 0620fddb56dfaf0e1034eeb69d79c73b361debbf Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Thu, 8 Jun 2017 14:49:26 +0100 Subject: [PATCH] KEYS: sanitize key structs before freeing While a 'struct key' itself normally does not contain sensitive information, Documentation/security/keys.txt actually encourages this: "Having a payload is not required; and the payload can, in fact, just be a value stored in the struct key itself." In case someone has taken this advice, or will take this advice in the future, zero the key structure before freeing it. We might as well, and as a bonus this could make it a bit more difficult for an adversary to determine which keys have recently been in use. This is safe because the key_jar cache does not use a constructor. Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: James Morris --- include/linux/key.h | 1 - security/keys/gc.c | 4 +--- 2 files changed, 1 insertion(+), 4 deletions(-) diff --git a/include/linux/key.h b/include/linux/key.h index 0c9b93b0d1f7..78e25aabedaf 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -173,7 +173,6 @@ struct key { #ifdef KEY_DEBUGGING unsigned magic; #define KEY_DEBUG_MAGIC 0x18273645u -#define KEY_DEBUG_MAGIC_X 0xf8e9dacbu #endif unsigned long flags; /* status flags (change with bitops) */ diff --git a/security/keys/gc.c b/security/keys/gc.c index 595becc6d0d2..87cb260e4890 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -158,9 +158,7 @@ static noinline void key_gc_unused_keys(struct list_head *keys) kfree(key->description); -#ifdef KEY_DEBUGGING - key->magic = KEY_DEBUG_MAGIC_X; -#endif + memzero_explicit(key, sizeof(*key)); kmem_cache_free(key_jar, key); } }