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From: Long Li <longli@microsoft.com>
To: Pavel Shilovsky <piastryyy@gmail.com>
Cc: Steve French <sfrench@samba.org>,
	linux-cifs <linux-cifs@vger.kernel.org>,
	samba-technical <samba-technical@lists.samba.org>,
	Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] cifs: Remove locking in smb2_verify_signature() when calculating SMB2/SMB3 signature on receiving packets
Date: Wed, 25 Mar 2020 23:29:43 +0000
Message-ID: <BN8PR21MB1155747496EDA5197AA3240DCECE0@BN8PR21MB1155.namprd21.prod.outlook.com> (raw)
In-Reply-To: <CAKywueQWcjWP7FNG0y-gGOSV5S1kSKJfWpspwXVzY9S2oHh+zQ@mail.gmail.com>

>Subject: Re: [PATCH] cifs: Remove locking in smb2_verify_signature() when
>calculating SMB2/SMB3 signature on receiving packets
>
>ср, 25 мар. 2020 г. в 11:15, <longli@linuxonhyperv.com>:
>>
>> From: Long Li <longli@microsoft.com>
>>
>> On the sending and receiving paths, CIFS uses the same cypto data
>> structures to calculate SMB2/SMB3 packet signatures. A lock on the
>> receiving path is necessary to control shared access to crypto data
>> structures. This lock degrades performance because it races with the
>sending path.
>>
>> Define separate crypto data structures for sending and receiving paths
>> and remove this lock.
>>
>> Signed-off-by: Long Li <longli@microsoft.com>
>> ---
>>  fs/cifs/cifsencrypt.c   |  29 +++++----
>>  fs/cifs/cifsglob.h      |  21 +++++--
>>  fs/cifs/smb2proto.h     |   4 +-
>>  fs/cifs/smb2transport.c | 130
>> +++++++++++++++++++++++++---------------
>>  4 files changed, 119 insertions(+), 65 deletions(-)
>>
>> diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c index
>> 97b7497c13ef..222e8d13302c 100644
>> --- a/fs/cifs/cifsencrypt.c
>> +++ b/fs/cifs/cifsencrypt.c
>> @@ -804,16 +804,27 @@ calc_seckey(struct cifs_ses *ses)  void
>> cifs_crypto_secmech_release(struct TCP_Server_Info *server)  {
>> -       if (server->secmech.cmacaes) {
>> -               crypto_free_shash(server->secmech.cmacaes);
>> -               server->secmech.cmacaes = NULL;
>> -       }
>> +       int i;
>> +
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               if (server->secmech.cmacaes[i]) {
>> +                       crypto_free_shash(server->secmech.cmacaes[i]);
>> +                       server->secmech.cmacaes[i] = NULL;
>> +               }
>>
>> -       if (server->secmech.hmacsha256) {
>> -               crypto_free_shash(server->secmech.hmacsha256);
>> -               server->secmech.hmacsha256 = NULL;
>> +               if (server->secmech.hmacsha256[i]) {
>> +                       crypto_free_shash(server->secmech.hmacsha256[i]);
>> +                       server->secmech.hmacsha256[i] = NULL;
>> +               }
>> +
>> +               kfree(server->secmech.sdesccmacaes[i]);
>> +               server->secmech.sdesccmacaes[i] = NULL;
>> +
>> +               kfree(server->secmech.sdeschmacsha256[i]);
>> +               server->secmech.sdeschmacsha256[i] = NULL;
>>         }
>>
>> +
>>         if (server->secmech.md5) {
>>                 crypto_free_shash(server->secmech.md5);
>>                 server->secmech.md5 = NULL; @@ -839,10 +850,6 @@
>> cifs_crypto_secmech_release(struct TCP_Server_Info *server)
>>                 server->secmech.ccmaesdecrypt = NULL;
>>         }
>>
>> -       kfree(server->secmech.sdesccmacaes);
>> -       server->secmech.sdesccmacaes = NULL;
>> -       kfree(server->secmech.sdeschmacsha256);
>> -       server->secmech.sdeschmacsha256 = NULL;
>>         kfree(server->secmech.sdeschmacmd5);
>>         server->secmech.sdeschmacmd5 = NULL;
>>         kfree(server->secmech.sdescmd5); diff --git
>> a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h index
>> 0d956360e984..e31a902ebadc 100644
>> --- a/fs/cifs/cifsglob.h
>> +++ b/fs/cifs/cifsglob.h
>> @@ -137,17 +137,27 @@ struct sdesc {
>>         char ctx[];
>>  };
>>
>> +enum {
>> +       CIFS_SECMECH_DIR_IN = 0,
>> +       CIFS_SECMECH_DIR_OUT,
>> +       CIFS_SECMECH_DIR_MAX
>> +};
>> +
>>  /* crypto hashing related structure/fields, not specific to a sec
>> mech */  struct cifs_secmech {
>>         struct crypto_shash *hmacmd5; /* hmac-md5 hash function */
>>         struct crypto_shash *md5; /* md5 hash function */
>> -       struct crypto_shash *hmacsha256; /* hmac-sha256 hash function */
>> -       struct crypto_shash *cmacaes; /* block-cipher based MAC function */
>> +       /* hmac-sha256 hash functions */
>> +       struct crypto_shash *hmacsha256[CIFS_SECMECH_DIR_MAX];
>> +       /* block-cipher based MAC function */
>> +       struct crypto_shash *cmacaes[CIFS_SECMECH_DIR_MAX];
>>         struct crypto_shash *sha512; /* sha512 hash function */
>>         struct sdesc *sdeschmacmd5;  /* ctxt to generate ntlmv2 hash, CR1 */
>>         struct sdesc *sdescmd5; /* ctxt to generate cifs/smb signature */
>> -       struct sdesc *sdeschmacsha256;  /* ctxt to generate smb2 signature */
>> -       struct sdesc *sdesccmacaes;  /* ctxt to generate smb3 signature */
>> +       /* ctxt to generate smb2 signature */
>> +       struct sdesc *sdeschmacsha256[CIFS_SECMECH_DIR_MAX];
>> +       /* ctxt to generate smb3 signature */
>> +       struct sdesc *sdesccmacaes[CIFS_SECMECH_DIR_MAX];
>>         struct sdesc *sdescsha512; /* ctxt to generate smb3.11 signing key */
>>         struct crypto_aead *ccmaesencrypt; /* smb3 encryption aead */
>>         struct crypto_aead *ccmaesdecrypt; /* smb3 decryption aead */
>> @@ -426,7 +436,8 @@ struct smb_version_operations {
>>         /* generate new lease key */
>>         void (*new_lease_key)(struct cifs_fid *);
>>         int (*generate_signingkey)(struct cifs_ses *);
>> -       int (*calc_signature)(struct smb_rqst *, struct TCP_Server_Info *);
>> +       int (*calc_signature)(struct smb_rqst *, struct TCP_Server_Info *,
>> +                             int direction);
>>         int (*set_integrity)(const unsigned int, struct cifs_tcon *tcon,
>>                              struct cifsFileInfo *src_file);
>>         int (*enum_snapshots)(const unsigned int xid, struct cifs_tcon
>> *tcon, diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h index
>> 4d1ff7b66fdc..f5edd6ea3639 100644
>> --- a/fs/cifs/smb2proto.h
>> +++ b/fs/cifs/smb2proto.h
>> @@ -55,9 +55,9 @@ extern struct cifs_ses *smb2_find_smb_ses(struct
>> TCP_Server_Info *server,  extern struct cifs_tcon
>*smb2_find_smb_tcon(struct TCP_Server_Info *server,
>>                                                 __u64 ses_id, __u32
>> tid);  extern int smb2_calc_signature(struct smb_rqst *rqst,
>> -                               struct TCP_Server_Info *server);
>> +                               struct TCP_Server_Info *server, int
>> + direction);
>>  extern int smb3_calc_signature(struct smb_rqst *rqst,
>> -                               struct TCP_Server_Info *server);
>> +                               struct TCP_Server_Info *server, int
>> + direction);
>>  extern void smb2_echo_request(struct work_struct *work);  extern
>> __le32 smb2_get_lease_state(struct cifsInodeInfo *cinode);  extern
>> bool smb2_is_valid_oplock_break(char *buffer, diff --git
>> a/fs/cifs/smb2transport.c b/fs/cifs/smb2transport.c index
>> 08b703b7a15e..c8ba40d8fedf 100644
>> --- a/fs/cifs/smb2transport.c
>> +++ b/fs/cifs/smb2transport.c
>> @@ -43,30 +43,51 @@
>>  static int
>>  smb2_crypto_shash_allocate(struct TCP_Server_Info *server)  {
>> -       return cifs_alloc_hash("hmac(sha256)",
>> -                              &server->secmech.hmacsha256,
>> -                              &server->secmech.sdeschmacsha256);
>> +       int i, rc;
>> +
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               rc = cifs_alloc_hash("hmac(sha256)",
>> +                              &server->secmech.hmacsha256[i],
>> +                              &server->secmech.sdeschmacsha256[i]);
>> +               if (rc)
>> +                       goto fail;
>> +       }
>> +       return 0;
>> +
>> +fail:
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++)
>> +               cifs_free_hash(
>> +                      &server->secmech.hmacsha256[i],
>> +                      &server->secmech.sdeschmacsha256[i]);
>> +       return rc;
>>  }
>>
>>  static int
>>  smb3_crypto_shash_allocate(struct TCP_Server_Info *server)  {
>>         struct cifs_secmech *p = &server->secmech;
>> -       int rc;
>> +       int i, rc;
>>
>> -       rc = cifs_alloc_hash("hmac(sha256)",
>> -                            &p->hmacsha256,
>> -                            &p->sdeschmacsha256);
>> -       if (rc)
>> -               goto err;
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               rc = cifs_alloc_hash("hmac(sha256)",
>> +                            &p->hmacsha256[i],
>> +                            &p->sdeschmacsha256[i]);
>> +               if (rc)
>> +                       goto fail;
>>
>> -       rc = cifs_alloc_hash("cmac(aes)", &p->cmacaes, &p->sdesccmacaes);
>> -       if (rc)
>> -               goto err;
>> +               rc = cifs_alloc_hash("cmac(aes)",
>> +                       &p->cmacaes[i], &p->sdesccmacaes[i]);
>>
>> +               if (rc)
>> +                       goto fail;
>> +       }
>>         return 0;
>> -err:
>> -       cifs_free_hash(&p->hmacsha256, &p->sdeschmacsha256);
>> +
>> +fail:
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               cifs_free_hash(&p->hmacsha256[i], &p->sdeschmacsha256[i]);
>> +               cifs_free_hash(&p->cmacaes[i], &p->sdesccmacaes[i]);
>> +       }
>>         return rc;
>>  }
>>
>> @@ -74,27 +95,32 @@ int
>>  smb311_crypto_shash_allocate(struct TCP_Server_Info *server)
>>  {
>>         struct cifs_secmech *p = &server->secmech;
>> -       int rc = 0;
>> +       int i, rc = 0;
>>
>> -       rc = cifs_alloc_hash("hmac(sha256)",
>> -                            &p->hmacsha256,
>> -                            &p->sdeschmacsha256);
>> -       if (rc)
>> -               return rc;
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               rc = cifs_alloc_hash("hmac(sha256)",
>> +                            &p->hmacsha256[i],
>> +                            &p->sdeschmacsha256[i]);
>> +               if (rc)
>> +                       goto fail;
>>
>> -       rc = cifs_alloc_hash("cmac(aes)", &p->cmacaes, &p->sdesccmacaes);
>> -       if (rc)
>> -               goto err;
>> +               rc = cifs_alloc_hash("cmac(aes)",
>> +                       &p->cmacaes[i], &p->sdesccmacaes[i]);
>> +               if (rc)
>> +                       goto fail;
>> +       }
>>
>>         rc = cifs_alloc_hash("sha512", &p->sha512, &p->sdescsha512);
>>         if (rc)
>> -               goto err;
>> +               goto fail;
>>
>>         return 0;
>>
>> -err:
>> -       cifs_free_hash(&p->cmacaes, &p->sdesccmacaes);
>> -       cifs_free_hash(&p->hmacsha256, &p->sdeschmacsha256);
>> +fail:
>> +       for (i = CIFS_SECMECH_DIR_IN; i < CIFS_SECMECH_DIR_MAX; i++) {
>> +               cifs_free_hash(&p->hmacsha256[i], &p->sdeschmacsha256[i]);
>> +               cifs_free_hash(&p->cmacaes[i], &p->sdesccmacaes[i]);
>> +       }
>>         return rc;
>>  }
>>
>> @@ -219,7 +245,8 @@ smb2_find_smb_tcon(struct TCP_Server_Info
>*server, __u64 ses_id, __u32  tid)
>>  }
>>
>>  int
>> -smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info
>*server)
>> +smb2_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info
>*server,
>> +                   int direction)
>>  {
>>         int rc;
>>         unsigned char smb2_signature[SMB2_HMACSHA256_SIZE];
>> @@ -229,6 +256,7 @@ smb2_calc_signature(struct smb_rqst *rqst, struct
>TCP_Server_Info *server)
>>         struct cifs_ses *ses;
>>         struct shash_desc *shash;
>>         struct smb_rqst drqst;
>> +       struct crypto_shash *hmacsha256;
>>
>>         ses = smb2_find_smb_ses(server, shdr->SessionId);
>>         if (!ses) {
>> @@ -245,14 +273,16 @@ smb2_calc_signature(struct smb_rqst *rqst, struct
>TCP_Server_Info *server)
>>                 return rc;
>>         }
>>
>> -       rc = crypto_shash_setkey(server->secmech.hmacsha256,
>> +       hmacsha256 = server->secmech.hmacsha256[direction];
>> +
>> +       rc = crypto_shash_setkey(hmacsha256,
>>                                  ses->auth_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with response\n",
>__func__);
>>                 return rc;
>>         }
>>
>> -       shash = &server->secmech.sdeschmacsha256->shash;
>> +       shash = &server->secmech.sdeschmacsha256[direction]->shash;
>>         rc = crypto_shash_init(shash);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not init sha256", __func__);
>> @@ -296,6 +326,8 @@ static int generate_key(struct cifs_ses *ses, struct
>kvec label,
>>         unsigned char prfhash[SMB2_HMACSHA256_SIZE];
>>         unsigned char *hashptr = prfhash;
>>         struct TCP_Server_Info *server = ses->server;
>> +       struct crypto_shash *hmacsha256;
>> +       struct sdesc *sdeschmacsha256;
>>
>>         memset(prfhash, 0x0, SMB2_HMACSHA256_SIZE);
>>         memset(key, 0x0, key_size);
>> @@ -306,55 +338,58 @@ static int generate_key(struct cifs_ses *ses, struct
>kvec label,
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_setkey(server->secmech.hmacsha256,
>> +       hmacsha256 = server-
>>secmech.hmacsha256[CIFS_SECMECH_DIR_OUT];
>> +       sdeschmacsha256 = server-
>>secmech.sdeschmacsha256[CIFS_SECMECH_DIR_OUT];
>> +
>> +       rc = crypto_shash_setkey(hmacsha256,
>>                 ses->auth_key.response, SMB2_NTLMV2_SESSKEY_SIZE);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not set with session key\n",
>__func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_init(&server->secmech.sdeschmacsha256->shash);
>> +       rc = crypto_shash_init(&sdeschmacsha256->shash);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not init sign hmac\n", __func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_update(&server->secmech.sdeschmacsha256-
>>shash,
>> +       rc = crypto_shash_update(&sdeschmacsha256->shash,
>>                                 i, 4);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with n\n", __func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_update(&server->secmech.sdeschmacsha256-
>>shash,
>> +       rc = crypto_shash_update(&sdeschmacsha256->shash,
>>                                 label.iov_base, label.iov_len);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with label\n",
>__func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_update(&server->secmech.sdeschmacsha256-
>>shash,
>> +       rc = crypto_shash_update(&sdeschmacsha256->shash,
>>                                 &zero, 1);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with zero\n",
>__func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_update(&server->secmech.sdeschmacsha256-
>>shash,
>> +       rc = crypto_shash_update(&sdeschmacsha256->shash,
>>                                 context.iov_base, context.iov_len);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with context\n",
>__func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_update(&server->secmech.sdeschmacsha256-
>>shash,
>> +       rc = crypto_shash_update(&sdeschmacsha256->shash,
>>                                 L, 4);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not update with L\n", __func__);
>>                 goto smb3signkey_ret;
>>         }
>>
>> -       rc = crypto_shash_final(&server->secmech.sdeschmacsha256->shash,
>> +       rc = crypto_shash_final(&sdeschmacsha256->shash,
>>                                 hashptr);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not generate sha256 hash\n",
>__func__);
>> @@ -504,16 +539,18 @@ generate_smb311signingkey(struct cifs_ses *ses)
>>  }
>>
>>  int
>> -smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info
>*server)
>> +smb3_calc_signature(struct smb_rqst *rqst, struct TCP_Server_Info
>*server,
>> +                   int direction)
>>  {
>>         int rc;
>>         unsigned char smb3_signature[SMB2_CMACAES_SIZE];
>>         unsigned char *sigptr = smb3_signature;
>>         struct kvec *iov = rqst->rq_iov;
>>         struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)iov[0].iov_base;
>> -       struct shash_desc *shash = &server->secmech.sdesccmacaes->shash;
>> +       struct shash_desc *shash;
>>         struct smb_rqst drqst;
>>         u8 key[SMB3_SIGN_KEY_SIZE];
>> +       struct crypto_shash *cmacaes;
>>
>>         rc = smb2_get_sign_key(shdr->SessionId, server, key);
>>         if (rc)
>> @@ -522,8 +559,10 @@ smb3_calc_signature(struct smb_rqst *rqst, struct
>TCP_Server_Info *server)
>>         memset(smb3_signature, 0x0, SMB2_CMACAES_SIZE);
>>         memset(shdr->Signature, 0x0, SMB2_SIGNATURE_SIZE);
>>
>> -       rc = crypto_shash_setkey(server->secmech.cmacaes,
>> -                                key, SMB2_CMACAES_SIZE);
>> +       cmacaes = server->secmech.cmacaes[direction];
>> +       shash = &server->secmech.sdesccmacaes[direction]->shash;
>> +
>> +       rc = crypto_shash_setkey(cmacaes, key, SMB2_CMACAES_SIZE);
>>         if (rc) {
>>                 cifs_server_dbg(VFS, "%s: Could not set key for cmac aes\n",
>__func__);
>>                 return rc;
>> @@ -593,8 +632,7 @@ smb2_sign_rqst(struct smb_rqst *rqst, struct
>TCP_Server_Info *server)
>>                 return 0;
>>         }
>>
>> -       rc = server->ops->calc_signature(rqst, server);
>> -
>> +       rc = server->ops->calc_signature(rqst, server,
>CIFS_SECMECH_DIR_OUT);
>>         return rc;
>>  }
>>
>> @@ -631,9 +669,7 @@ smb2_verify_signature(struct smb_rqst *rqst, struct
>TCP_Server_Info *server)
>>
>>         memset(shdr->Signature, 0, SMB2_SIGNATURE_SIZE);
>>
>> -       mutex_lock(&server->srv_mutex);
>> -       rc = server->ops->calc_signature(rqst, server);
>> -       mutex_unlock(&server->srv_mutex);
>> +       rc = server->ops->calc_signature(rqst, server, CIFS_SECMECH_DIR_IN);
>
>Multiple threads may be calling smb2_verify_signature from
>smb2_check_receive in separate threads (see compound_send_recv). What
>will prevent races on crypto data structures once the mutex around
>calc_signature is removed?

It's my bad I will fix it. In this case we need another mutex for the receiving paths. I was looking at smb2_writev_callback() and smb2_readv_callback(), they are called from cifsd and also use this mutex. This mutex does the most damage in those two callback functions as it may block the receiving thread.

Thanks,
Long

>
>--
>Best regards,
>Pavel Shilovsky

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25 18:13 longli
2020-03-25 21:39 ` Pavel Shilovsky
2020-03-25 23:29   ` Long Li [this message]
2020-03-26  1:37     ` Steve French
2020-03-26  1:57       ` Long Li
2020-03-26  9:56 ` Aurélien Aptel
2020-03-27  5:41   ` Long Li
2020-03-27 11:05     ` Aurélien Aptel

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