From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f196.google.com ([209.85.223.196]:56825 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751354AbdJXT0Y (ORCPT ); Tue, 24 Oct 2017 15:26:24 -0400 Received: by mail-io0-f196.google.com with SMTP id m81so25055740ioi.13 for ; Tue, 24 Oct 2017 12:26:24 -0700 (PDT) From: Eric Biggers To: stable@vger.kernel.org Cc: Eric Biggers , David Howells Subject: [PATCH] fscrypt: fix dereference of NULL user_key_payload Date: Tue, 24 Oct 2017 12:26:04 -0700 Message-Id: <20171024192604.57798-1-ebiggers3@gmail.com> Sender: stable-owner@vger.kernel.org List-ID: From: Eric Biggers 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 Cc: [v4.1+] Signed-off-by: Eric Biggers Signed-off-by: David Howells --- 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fscrypt_info *crypt_info, goto out; } ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + goto out; + } if (ukp-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