3.16.52-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
commit f66665c09ab489a11ca490d6a82df57cfc1bea3e upstream.
In eCryptfs, we failed to verify that the authentication token keys are not revoked before dereferencing their payloads, which is problematic because the payload of a revoked key is NULL. request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we acquire the key semaphore.
Fix it by updating ecryptfs_get_key_payload_data() to return -EKEYREVOKED if the key payload is NULL. For completeness we check this for "encrypted" keys as well as "user" keys, although encrypted keys cannot be revoked currently.
Alternatively we could use key_validate(), but since we'll also need to fix ecryptfs_get_key_payload_data() to validate the payload length, it seems appropriate to just check the payload pointer.
Fixes: 237fead61998 ("[PATCH] ecryptfs: fs/Makefile and fs/Kconfig") Reviewed-by: James Morris james.l.morris@oracle.com Cc: Michael Halcrow mhalcrow@google.com Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: David Howells dhowells@redhat.com [bwh: Backported to 3.16: user key payload is key->payload.data, not key->payload.data[0]] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/fs/ecryptfs/ecryptfs_kernel.h +++ b/fs/ecryptfs/ecryptfs_kernel.h @@ -84,11 +84,16 @@ struct ecryptfs_page_crypt_context { static inline struct ecryptfs_auth_tok * ecryptfs_get_encrypted_key_payload_data(struct key *key) { - if (key->type == &key_type_encrypted) - return (struct ecryptfs_auth_tok *) - (&((struct encrypted_key_payload *)key->payload.data)->payload_data); - else + struct encrypted_key_payload *payload; + + if (key->type != &key_type_encrypted) return NULL; + + payload = key->payload.data; + if (!payload) + return ERR_PTR(-EKEYREVOKED); + + return (struct ecryptfs_auth_tok *)payload->payload_data; }
static inline struct key *ecryptfs_get_encrypted_key(char *sig) @@ -114,13 +119,17 @@ static inline struct ecryptfs_auth_tok * ecryptfs_get_key_payload_data(struct key *key) { struct ecryptfs_auth_tok *auth_tok; + struct user_key_payload *ukp;
auth_tok = ecryptfs_get_encrypted_key_payload_data(key); - if (!auth_tok) - return (struct ecryptfs_auth_tok *) - (((struct user_key_payload *)key->payload.data)->data); - else + if (auth_tok) return auth_tok; + + ukp = key->payload.data; + if (!ukp) + return ERR_PTR(-EKEYREVOKED); + + return (struct ecryptfs_auth_tok *)ukp->data; }
#define ECRYPTFS_MAX_KEYSET_SIZE 1024 --- a/fs/ecryptfs/keystore.c +++ b/fs/ecryptfs/keystore.c @@ -459,7 +459,8 @@ out: * @auth_tok_key: key containing the authentication token * @auth_tok: authentication token * - * Returns zero on valid auth tok; -EINVAL otherwise + * Returns zero on valid auth tok; -EINVAL if the payload is invalid; or + * -EKEYREVOKED if the key was revoked before we acquired its semaphore. */ static int ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key, @@ -468,6 +469,12 @@ ecryptfs_verify_auth_tok_from_key(struct int rc = 0;
(*auth_tok) = ecryptfs_get_key_payload_data(auth_tok_key); + if (IS_ERR(*auth_tok)) { + rc = PTR_ERR(*auth_tok); + *auth_tok = NULL; + goto out; + } + if (ecryptfs_verify_version((*auth_tok)->version)) { printk(KERN_ERR "Data structure version mismatch. Userspace " "tools must match eCryptfs kernel module with major "