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From:   Long Li <longli@microsoft.com>
To:     "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
        Steve French <sfrench@samba.org>,
        "linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
        "samba-technical@lists.samba.org" <samba-technical@lists.samba.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
CC:     "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [Patch v2 2/6] cifs: Allocate validate negotiation request
 through kmalloc
Thread-Topic: [Patch v2 2/6] cifs: Allocate validate negotiation request
 through kmalloc
Thread-Index: AQHT1oDi/JtXjb7nnEuffEhFIifliqQHQlkAgAAAvYA=
Date:   Thu, 19 Apr 2018 00:48:57 +0000
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 <20180417191710.14855-2-longli@linuxonhyperv.com>
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> Subject: RE: [Patch v2 2/6] cifs: Allocate validate negotiation request t=
hrough
> kmalloc
>=20
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org
> > <linux-kernel-owner@vger.kernel.org> On Behalf Of Long Li
> > Sent: Tuesday, April 17, 2018 12:17 PM
> > To: Steve French <sfrench@samba.org>; linux-cifs@vger.kernel.org;
> > samba- technical@lists.samba.org; linux-kernel@vger.kernel.org;
> > linux-rdma@vger.kernel.org
> > Cc: Long Li <longli@microsoft.com>; stable@vger.kernel.org
> > Subject: [Patch v2 2/6] cifs: Allocate validate negotiation request
> > through kmalloc
> >
> > From: Long Li <longli@microsoft.com>
> >
> > The data buffer allocated on the stack can't be DMA'ed, and hence
> > can't send through RDMA via SMB Direct.
> >
> > Fix this by allocating the request on the heap in smb3_validate_negotia=
te.
> >
> > Fixes: ff1c038addc4f205d5f1ede449426c7d316c0eed "Check SMB3 dialects
> > against downgrade attacks"
> >
> > Changes in v2:
> > Removed duplicated code on freeing buffers on function exit.
> > (Thanks to Parav Pandit <parav@mellanox.com>)
> >
> > Fixed typo in the patch title.
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> > Cc: stable@vger.kernel.org
> > ---
> >  fs/cifs/smb2pdu.c | 57
> > ++++++++++++++++++++++++++++++-------------------------
> >  1 file changed, 31 insertions(+), 26 deletions(-)
> >
> > diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index
> > 0f044c4..41625e4 100644
> > --- a/fs/cifs/smb2pdu.c
> > +++ b/fs/cifs/smb2pdu.c
> > @@ -729,8 +729,8 @@ SMB2_negotiate(const unsigned int xid, struct
> > cifs_ses *ses)
> >
> >  int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon
> > *tcon)  {
> > -	int rc =3D 0;
> > -	struct validate_negotiate_info_req vneg_inbuf;
> > +	int ret, rc =3D -EIO;
> > +	struct validate_negotiate_info_req *pneg_inbuf;
> >  	struct validate_negotiate_info_rsp *pneg_rsp =3D NULL;
> >  	u32 rsplen;
> >  	u32 inbuflen; /* max of 4 dialects */ @@ -741,6 +741,9 @@ int
> > smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon
> > *tcon)
> >  	if (tcon->ses->server->rdma)
> >  		return 0;
> >  #endif
> > +	pneg_inbuf =3D kmalloc(sizeof(*pneg_inbuf), GFP_KERNEL);
> > +	if (!pneg_inbuf)
> > +		return -ENOMEM;
>=20
> Immediately after the above new code, there are three if statements that
> can 'return 0' and never free the pneg_inbuf memory.  They should instead
> set 'rc'
> appropriately and 'goto' the out_free_inbuf label.

Thanks!

I will move the kmalloc after those statements.

>=20
> Michael
>=20
> >
> >  	/* In SMB3.11 preauth integrity supersedes validate negotiate */
> >  	if (tcon->ses->server->dialect =3D=3D SMB311_PROT_ID) @@ -764,53
> +767,53
> > @@ int smb3_validate_negotiate(const unsigned int xid, struct
> > cifs_tcon
> > *tcon)
> >  	if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_NULL)
> >  		cifs_dbg(VFS, "Unexpected null user (anonymous) auth flag
> sent by
> > server\n");
> >
> > -	vneg_inbuf.Capabilities =3D
> > +	pneg_inbuf->Capabilities =3D
> >  			cpu_to_le32(tcon->ses->server->vals-
> >req_capabilities);
> > -	memcpy(vneg_inbuf.Guid, tcon->ses->server->client_guid,
> > +	memcpy(pneg_inbuf->Guid, tcon->ses->server->client_guid,
> >  					SMB2_CLIENT_GUID_SIZE);
> >
> >  	if (tcon->ses->sign)
> > -		vneg_inbuf.SecurityMode =3D
> > +		pneg_inbuf->SecurityMode =3D
> >
> 	cpu_to_le16(SMB2_NEGOTIATE_SIGNING_REQUIRED);
> >  	else if (global_secflags & CIFSSEC_MAY_SIGN)
> > -		vneg_inbuf.SecurityMode =3D
> > +		pneg_inbuf->SecurityMode =3D
> >
> 	cpu_to_le16(SMB2_NEGOTIATE_SIGNING_ENABLED);
> >  	else
> > -		vneg_inbuf.SecurityMode =3D 0;
> > +		pneg_inbuf->SecurityMode =3D 0;
> >
> >
> >  	if (strcmp(tcon->ses->server->vals->version_string,
> >  		SMB3ANY_VERSION_STRING) =3D=3D 0) {
> > -		vneg_inbuf.Dialects[0] =3D cpu_to_le16(SMB30_PROT_ID);
> > -		vneg_inbuf.Dialects[1] =3D cpu_to_le16(SMB302_PROT_ID);
> > -		vneg_inbuf.DialectCount =3D cpu_to_le16(2);
> > +		pneg_inbuf->Dialects[0] =3D cpu_to_le16(SMB30_PROT_ID);
> > +		pneg_inbuf->Dialects[1] =3D cpu_to_le16(SMB302_PROT_ID);
> > +		pneg_inbuf->DialectCount =3D cpu_to_le16(2);
> >  		/* structure is big enough for 3 dialects, sending only 2 */
> >  		inbuflen =3D sizeof(struct validate_negotiate_info_req) - 2;
> >  	} else if (strcmp(tcon->ses->server->vals->version_string,
> >  		SMBDEFAULT_VERSION_STRING) =3D=3D 0) {
> > -		vneg_inbuf.Dialects[0] =3D cpu_to_le16(SMB21_PROT_ID);
> > -		vneg_inbuf.Dialects[1] =3D cpu_to_le16(SMB30_PROT_ID);
> > -		vneg_inbuf.Dialects[2] =3D cpu_to_le16(SMB302_PROT_ID);
> > -		vneg_inbuf.DialectCount =3D cpu_to_le16(3);
> > +		pneg_inbuf->Dialects[0] =3D cpu_to_le16(SMB21_PROT_ID);
> > +		pneg_inbuf->Dialects[1] =3D cpu_to_le16(SMB30_PROT_ID);
> > +		pneg_inbuf->Dialects[2] =3D cpu_to_le16(SMB302_PROT_ID);
> > +		pneg_inbuf->DialectCount =3D cpu_to_le16(3);
> >  		/* structure is big enough for 3 dialects */
> >  		inbuflen =3D sizeof(struct validate_negotiate_info_req);
> >  	} else {
> >  		/* otherwise specific dialect was requested */
> > -		vneg_inbuf.Dialects[0] =3D
> > +		pneg_inbuf->Dialects[0] =3D
> >  			cpu_to_le16(tcon->ses->server->vals->protocol_id);
> > -		vneg_inbuf.DialectCount =3D cpu_to_le16(1);
> > +		pneg_inbuf->DialectCount =3D cpu_to_le16(1);
> >  		/* structure is big enough for 3 dialects, sending only 1 */
> >  		inbuflen =3D sizeof(struct validate_negotiate_info_req) - 4;
> >  	}
> >
> > -	rc =3D SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
> > +	ret =3D SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
> >  		FSCTL_VALIDATE_NEGOTIATE_INFO, true /* is_fsctl */,
> > -		(char *)&vneg_inbuf, sizeof(struct
> validate_negotiate_info_req),
> > +		(char *)pneg_inbuf, sizeof(struct
> validate_negotiate_info_req),
> >  		(char **)&pneg_rsp, &rsplen);
> >
> > -	if (rc !=3D 0) {
> > -		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
> > -		return -EIO;
> > +	if (ret !=3D 0) {
> > +		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", ret);
> > +		goto out_free_inbuf;
> >  	}
> >
> >  	if (rsplen !=3D sizeof(struct validate_negotiate_info_rsp)) { @@
> > -820,7 +823,7 @@ int smb3_validate_negotiate(const unsigned int xid,
> > struct cifs_tcon
> > *tcon)
> >  		/* relax check since Mac returns max bufsize allowed on ioctl
> */
> >  		if ((rsplen > CIFSMaxBufSize)
> >  		     || (rsplen < sizeof(struct validate_negotiate_info_rsp)))
> > -			goto err_rsp_free;
> > +			goto out_free_rsp;
> >  	}
> >
> >  	/* check validate negotiate info response matches what we got
> > earlier */ @@ -838,14 +841,16 @@ int smb3_validate_negotiate(const
> > unsigned int xid, struct cifs_tcon
> > *tcon)
> >
> >  	/* validate negotiate successful */
> >  	cifs_dbg(FYI, "validate negotiate info successful\n");
> > -	kfree(pneg_rsp);
> > -	return 0;
> > +	rc =3D 0;
> > +	goto out_free_rsp;
> >
> >  vneg_out:
> >  	cifs_dbg(VFS, "protocol revalidation - security settings
> > mismatch\n");
> > -err_rsp_free:
> > +out_free_rsp:
> >  	kfree(pneg_rsp);
> > -	return -EIO;
> > +out_free_inbuf:
> > +	kfree(pneg_inbuf);
> > +	return rc;
> >  }
> >
> >  enum securityEnum
> > --
> > 2.7.4