RE: [Patch v3 2/6] cifs: Allocate validate negotiation request through kmalloc

[Long Li]

> Subject: Re: [Patch v3 2/6] cifs: Allocate validate negotiation request through
> kmalloc
> 
> On 4/18/2018 1:16 PM, Long Li wrote:
> >> Subject: Re: [Patch v3 2/6] cifs: Allocate validate negotiation
> >> request through kmalloc
> >>
> >> Two comments.
> >>
> >> On 4/17/2018 8:33 PM, Long Li wrote:
> >>> From: Long Li <longli@xxxxxxxxxxxxx>
> >>>
> >>> The data buffer allocated on the stack can't be DMA'ed, and hence
> >>> can't send through RDMA via SMB Direct.
> >>
> >> This comment is confusing. Any registered memory can be DMA'd, need
> >> to state the reason for the choice here more clearly.
> >>
> >>>
> >>> Fix this by allocating the request on the heap in
> smb3_validate_negotiate.
> >>>
> >>> Changes in v2:
> >>> Removed duplicated code on freeing buffers on function exit.
> >>> (Thanks to Parav Pandit <parav@xxxxxxxxxxxx>) Fixed typo in the
> >>> patch title.
> >>>
> >>> Changes in v3:
> >>> Added "Fixes" to the patch.
> >>> Changed sizeof() to use *pointer in place of struct.
> >>>
> >>> Fixes: ff1c038addc4 ("Check SMB3 dialects against downgrade
> >>> attacks")
> >>> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> >>> Cc: stable@xxxxxxxxxxxxxxx
> >>> ---
> >>>    fs/cifs/smb2pdu.c | 59
> >>> ++++++++++++++++++++++++++++++--------------
> >> -----------
> >>>    1 file changed, 32 insertions(+), 27 deletions(-)
> >>>
> >>> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index
> >>> 0f044c4..5582a02 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 = 0;
> >>> -	struct validate_negotiate_info_req vneg_inbuf;
> >>> +	int ret, rc = -EIO;
> >>> +	struct validate_negotiate_info_req *pneg_inbuf;
> >>>    	struct validate_negotiate_info_rsp *pneg_rsp = 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 = kmalloc(sizeof(*pneg_inbuf), GFP_KERNEL);
> >>> +	if (!pneg_inbuf)
> >>> +		return -ENOMEM;
> >>
> >> Why is this a nonblocking allocation? It would seem more robust to
> >> use GFP_NOFS here.
> >
> > I agree it makes sense to use GFP_NOFS.
> >
> > The choice here is made consistent with all the rest CIFS code allocating
> protocol request buffers. Maybe we should do another patch to cleanup all
> those code.
> 
> It'll be required sooner or later. I'm agnostic as to how you apply it, but I still
> suggest you change this one now rather than continue the fragile behavior. It
> may not be a global search-and-replace since some allocations may require
> nonblocking.

Okay, I will fix this.

> 
> 
> >
> >>
> >> Tom.
> >>
> >>>
> >>>    	/* In SMB3.11 preauth integrity supersedes validate negotiate */
> >>>    	if (tcon->ses->server->dialect == SMB311_PROT_ID) @@ -764,63
> >>> +767,63 @@ 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 =
> >>> +	pneg_inbuf->Capabilities =
> >>>    			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 =
> >>> +		pneg_inbuf->SecurityMode =
> >>>
> >> 	cpu_to_le16(SMB2_NEGOTIATE_SIGNING_REQUIRED);
> >>>    	else if (global_secflags & CIFSSEC_MAY_SIGN)
> >>> -		vneg_inbuf.SecurityMode =
> >>> +		pneg_inbuf->SecurityMode =
> >>>
> >> 	cpu_to_le16(SMB2_NEGOTIATE_SIGNING_ENABLED);
> >>>    	else
> >>> -		vneg_inbuf.SecurityMode = 0;
> >>> +		pneg_inbuf->SecurityMode = 0;
> >>>
> >>>
> >>>    	if (strcmp(tcon->ses->server->vals->version_string,
> >>>    		SMB3ANY_VERSION_STRING) == 0) {
> >>> -		vneg_inbuf.Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
> >>> -		vneg_inbuf.Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
> >>> -		vneg_inbuf.DialectCount = cpu_to_le16(2);
> >>> +		pneg_inbuf->Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
> >>> +		pneg_inbuf->Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
> >>> +		pneg_inbuf->DialectCount = cpu_to_le16(2);
> >>>    		/* structure is big enough for 3 dialects, sending only 2 */
> >>>    		inbuflen = sizeof(struct validate_negotiate_info_req) - 2;
> >>>    	} else if (strcmp(tcon->ses->server->vals->version_string,
> >>>    		SMBDEFAULT_VERSION_STRING) == 0) {
> >>> -		vneg_inbuf.Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
> >>> -		vneg_inbuf.Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
> >>> -		vneg_inbuf.Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
> >>> -		vneg_inbuf.DialectCount = cpu_to_le16(3);
> >>> +		pneg_inbuf->Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
> >>> +		pneg_inbuf->Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
> >>> +		pneg_inbuf->Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
> >>> +		pneg_inbuf->DialectCount = cpu_to_le16(3);
> >>>    		/* structure is big enough for 3 dialects */
> >>>    		inbuflen = sizeof(struct validate_negotiate_info_req);
> >>>    	} else {
> >>>    		/* otherwise specific dialect was requested */
> >>> -		vneg_inbuf.Dialects[0] =
> >>> +		pneg_inbuf->Dialects[0] =
> >>>    			cpu_to_le16(tcon->ses->server->vals->protocol_id);
> >>> -		vneg_inbuf.DialectCount = cpu_to_le16(1);
> >>> +		pneg_inbuf->DialectCount = cpu_to_le16(1);
> >>>    		/* structure is big enough for 3 dialects, sending only 1 */
> >>>    		inbuflen = sizeof(struct validate_negotiate_info_req) - 4;
> >>>    	}
> >>>
> >>> -	rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
> >>> +	ret = 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(*pneg_inbuf),
> >>>    		(char **)&pneg_rsp, &rsplen);
> >>>
> >>> -	if (rc != 0) {
> >>> -		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
> >>> -		return -EIO;
> >>> +	if (ret) {
> >>> +		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", ret);
> >>> +		goto out_free_inbuf;
> >>>    	}
> >>>
> >>> -	if (rsplen != sizeof(struct validate_negotiate_info_rsp)) {
> >>> +	if (rsplen != sizeof(*pneg_rsp)) {
> >>>    		cifs_dbg(VFS, "invalid protocol negotiate response
> >> size: %d\n",
> >>>    			 rsplen);
> >>>
> >>>    		/* 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 = 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
> >>>
> > N     r  y   b X  Çv ^ )Þ{.n +    {  Ù {ay ÊÚ ,j   f   h   z  w
> 
>    j:+v   w j m         zZ+     Ýj"  !tml=
> >