From 94efe72f762e2c147d8146d637d5ece5614c8d94 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 4 Aug 2005 13:07:07 -0700 Subject: [PATCH] [PATCH] Destruction of failed keyring oopses The attached patch makes sure that a keyring that failed to instantiate properly is destroyed without oopsing [CAN-2005-2099]. The problem occurs in three stages: (1) The key allocator initialises the type-specific data to all zeroes. In the case of a keyring, this will become a link in the keyring name list when the keyring is instantiated. (2) If a user (any user) attempts to add a keyring with anything other than an empty payload, the keyring instantiation function will fail with an error and won't add the keyring to the name list. (3) The keyring's destructor then sees that the keyring has a description (name) and tries to remove the keyring from the name list, which oopses because the link pointers are both zero. This bug permits any user to take down a box trivially. Signed-Off-By: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/keys/keyring.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/security/keys/keyring.c b/security/keys/keyring.c index a1f6bac647a1..9c208c756df8 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -201,7 +201,11 @@ static void keyring_destroy(struct key *keyring) if (keyring->description) { write_lock(&keyring_name_lock); - list_del(&keyring->type_data.link); + + if (keyring->type_data.link.next != NULL && + !list_empty(&keyring->type_data.link)) + list_del(&keyring->type_data.link); + write_unlock(&keyring_name_lock); } -- 2.20.1