The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d60b5b7854c3d135b869f74fb93eaf63cbb1991a Mon Sep 17 00:00:00 2001 From: Eric Biggers <ebiggers@xxxxxxxxxx> Date: Mon, 9 Oct 2017 12:46:18 -0700 Subject: [PATCH] fscrypt: fix dereference of NULL user_key_payload 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> 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fscrypt_info *crypt_info, goto out; } ukp = user_key_payload_locked(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + goto out; + } if (ukp-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;