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authorEric Biggers <ebiggers@google.com>2017-10-09 12:37:49 -0700
committerDavid Howells <dhowells@redhat.com>2017-10-12 15:55:09 +0100
commit13923d0865ca96312197962522e88bc0aedccd74 (patch)
treebf7441d098bd2f41ca7f2fa92010d6b59291b548
parent9e66317d3c92ddaab330c125dfe9d06eee268aff (diff)
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KEYS: encrypted: fix dereference of NULL user_key_payload
A key of type "encrypted" references a "master key" which is used to encrypt and decrypt the encrypted key's payload. However, when we accessed the master key's payload, we failed to handle the case where the master key has been revoked, which sets the payload pointer to NULL. Note that request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we acquire its semaphore. Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested. This was an issue for master keys of type "user" only. Master keys can also be of type "trusted", but those cannot be revoked. Fixes: 7e70cb497850 ("keys: add new key-type encrypted") Reviewed-by: James Morris <james.l.morris@oracle.com> Cc: <stable@vger.kernel.org> [v2.6.38+] Cc: Mimi Zohar <zohar@linux.vnet.ibm.com> Cc: David Safford <safford@us.ibm.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com>
-rw-r--r--security/keys/encrypted-keys/encrypted.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 69855ba0d3b3..535db141f4da 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -309,6 +309,13 @@ static struct key *request_user_key(const char *master_desc, const u8 **master_k
down_read(&ukey->sem);
upayload = user_key_payload_locked(ukey);
+ if (!upayload) {
+ /* key was revoked before we acquired its semaphore */
+ up_read(&ukey->sem);
+ key_put(ukey);
+ ukey = ERR_PTR(-EKEYREVOKED);
+ goto error;
+ }
*master_key = upayload->data;
*master_keylen = upayload->datalen;
error: