From: Eric Biggers <ebiggers@xxxxxxxxxx>
When an fscrypt-encrypted file is opened, we request the file's master
key from the keyrings service as a logon key, then access its payload.
However, a revoked key has a NULL payload, and we failed to check for
this. 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.
Fixes: 88bd6ccdcdd6 ("ext4 crypto: add encryption key management facilities")
Reviewed-by: James Morris <james.l.morris@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [v4.1+]
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/crypto/keyinfo.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index 018c588c7ac3..8e704d12a1cf 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -109,6 +109,11 @@ static int validate_user_key(struct fscrypt_info *crypt_info,
goto out;
}
ukp = user_key_payload_locked(keyring_key);
+ if (!ukp) {
+ /* key was revoked before we acquired its semaphore */
+ res = -EKEYREVOKED;
+ goto out;
+ }
if (ukp->datalen != sizeof(struct fscrypt_key)) {
res = -EINVAL;
goto out;