From 61cfac6f267dabcf2740a7ec8a0295833b28b5f5 Mon Sep 17 00:00:00 2001 From: Pavel Shilovsky Date: Tue, 28 Feb 2017 16:05:19 -0800 Subject: [PATCH] CIFS: Fix possible use after free in demultiplex thread The recent changes that added SMB3 encryption support introduced a possible use after free in the demultiplex thread. When we process an encrypted packed we obtain a pointer to SMB session but do not obtain a reference. This can possibly lead to a situation when this session was freed before we copy a decryption key from there. Fix this by obtaining a copy of the key rather than a pointer to the session under a spinlock. Signed-off-by: Pavel Shilovsky Signed-off-by: Steve French --- fs/cifs/smb2ops.c | 32 ++++++++++++++++++++++++++------ 1 file changed, 26 insertions(+), 6 deletions(-) diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index a44b4dbe4aae..d2cdd9c19d17 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -1609,6 +1609,26 @@ static void cifs_crypt_complete(struct crypto_async_request *req, int err) complete(&res->completion); } +static int +smb2_get_enc_key(struct TCP_Server_Info *server, __u64 ses_id, int enc, u8 *key) +{ + struct cifs_ses *ses; + u8 *ses_enc_key; + + spin_lock(&cifs_tcp_ses_lock); + list_for_each_entry(ses, &server->smb_ses_list, smb_ses_list) { + if (ses->Suid != ses_id) + continue; + ses_enc_key = enc ? ses->smb3encryptionkey : + ses->smb3decryptionkey; + memcpy(key, ses_enc_key, SMB3_SIGN_KEY_SIZE); + spin_unlock(&cifs_tcp_ses_lock); + return 0; + } + spin_unlock(&cifs_tcp_ses_lock); + + return 1; +} /* * Encrypt or decrypt @rqst message. @rqst has the following format: * iov[0] - transform header (associate data), @@ -1622,10 +1642,10 @@ crypt_message(struct TCP_Server_Info *server, struct smb_rqst *rqst, int enc) struct smb2_transform_hdr *tr_hdr = (struct smb2_transform_hdr *)rqst->rq_iov[0].iov_base; unsigned int assoc_data_len = sizeof(struct smb2_transform_hdr) - 24; - struct cifs_ses *ses; int rc = 0; struct scatterlist *sg; u8 sign[SMB2_SIGNATURE_SIZE] = {}; + u8 key[SMB3_SIGN_KEY_SIZE]; struct aead_request *req; char *iv; unsigned int iv_len; @@ -1635,9 +1655,10 @@ crypt_message(struct TCP_Server_Info *server, struct smb_rqst *rqst, int enc) init_completion(&result.completion); - ses = smb2_find_smb_ses(server, tr_hdr->SessionId); - if (!ses) { - cifs_dbg(VFS, "%s: Could not find session\n", __func__); + rc = smb2_get_enc_key(server, tr_hdr->SessionId, enc, key); + if (rc) { + cifs_dbg(VFS, "%s: Could not get %scryption key\n", __func__, + enc ? "en" : "de"); return 0; } @@ -1649,8 +1670,7 @@ crypt_message(struct TCP_Server_Info *server, struct smb_rqst *rqst, int enc) tfm = enc ? server->secmech.ccmaesencrypt : server->secmech.ccmaesdecrypt; - rc = crypto_aead_setkey(tfm, enc ? ses->smb3encryptionkey : - ses->smb3decryptionkey, SMB3_SIGN_KEY_SIZE); + rc = crypto_aead_setkey(tfm, key, SMB3_SIGN_KEY_SIZE); if (rc) { cifs_dbg(VFS, "%s: Failed to set aead key %d\n", __func__, rc); return rc; -- 2.20.1