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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: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <smfrench@gmail.com>
zero-colors
Pavel Shilovsky 2017-02-28 16:05:19 -08:00 committed by Steve French
parent 6053dc9814
commit 61cfac6f26
1 changed files with 26 additions and 6 deletions
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32
fs/cifs/smb2ops.c
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@ -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;