Commit 61cfac6f authored by Pavel Shilovsky's avatar Pavel Shilovsky Committed by Steve French
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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: default avatarPavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: default avatarSteve French <smfrench@gmail.com>
parent 6053dc98

fs/cifs/smb2ops.c

+26 −6
Original line number Diff line number Diff line
@@ -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;

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