Commit 0620fddb authored Jun 08, 2017 by Eric Biggers Committed by James Morris Jun 09, 2017

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 <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>

parent ee618b46

include/linux/key.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -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) */

security/keys/gc.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -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);
		}
		}

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