From: Eric Biggers <ebiggers@xxxxxxxxxx> commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream. Please apply to 4.9-stable. 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 bb4606368eb1..a755fa1a0017 100644 --- a/fs/crypto/keyinfo.c +++ b/fs/crypto/keyinfo.c @@ -108,6 +108,11 @@ static int validate_user_key(struct fscrypt_info *crypt_info, goto out; } ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + goto out; + } if (ukp-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; -- 2.15.0.rc0.271.g36b669edcc-goog