From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f67.google.com ([209.85.214.67]:46982 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751522AbdJXTbN (ORCPT ); Tue, 24 Oct 2017 15:31:13 -0400 Received: by mail-it0-f67.google.com with SMTP id f187so11377889itb.1 for ; Tue, 24 Oct 2017 12:31:13 -0700 (PDT) From: Eric Biggers To: stable@vger.kernel.org Cc: Theodore Ts'o , Jaegeuk Kim , David Howells , Eric Biggers Subject: [PATCH 3/3] fscrypt: fix dereference of NULL user_key_payload Date: Tue, 24 Oct 2017 12:30:03 -0700 Message-Id: <20171024193003.58499-3-ebiggers3@gmail.com> In-Reply-To: <20171024193003.58499-1-ebiggers3@gmail.com> References: <20171024193003.58499-1-ebiggers3@gmail.com> Sender: stable-owner@vger.kernel.org List-ID: From: Eric Biggers commit d60b5b7854c3d135b869f74fb93eaf63cbb1991a upstream. Please apply to 4.4-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/ext4/crypto_key.c | 6 ++++++ fs/f2fs/crypto_key.c | 6 ++++++ 2 files changed, 12 insertions(+) diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c index 505f8afde57c..9a1bc638abce 100644 --- a/fs/ext4/crypto_key.c +++ b/fs/ext4/crypto_key.c @@ -204,6 +204,12 @@ int ext4_get_encryption_info(struct inode *inode) } down_read(&keyring_key->sem); ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + up_read(&keyring_key->sem); + goto out; + } if (ukp->datalen != sizeof(struct ext4_encryption_key)) { res = -EINVAL; up_read(&keyring_key->sem); diff --git a/fs/f2fs/crypto_key.c b/fs/f2fs/crypto_key.c index ae49be377b60..7e62889a1d3d 100644 --- a/fs/f2fs/crypto_key.c +++ b/fs/f2fs/crypto_key.c @@ -195,6 +195,12 @@ int f2fs_get_encryption_info(struct inode *inode) } down_read(&keyring_key->sem); ukp = user_key_payload(keyring_key); + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + res = -EKEYREVOKED; + up_read(&keyring_key->sem); + goto out; + } if (ukp->datalen != sizeof(struct f2fs_encryption_key)) { res = -EINVAL; up_read(&keyring_key->sem); -- 2.15.0.rc0.271.g36b669edcc-goog