Re: [PATCH 2/6] cifs: Allocate validate negoation request through kmalloc

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Apr 16, 2018 at 05:49:14PM -0700, Long Li wrote:
> 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_negotiate.
> 
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  fs/cifs/smb2pdu.c | 38 ++++++++++++++++++++++----------------
>  1 file changed, 22 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 0f044c4..abbefe2 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -730,7 +730,7 @@ 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;
> +	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;
>  
>  	/* In SMB3.11 preauth integrity supersedes validate negotiate */
>  	if (tcon->ses->server->dialect == SMB311_PROT_ID)
> @@ -764,52 +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 =
> +	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,
>  		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 != 0) {
>  		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
> +		kfree(pneg_inbuf);
>  		return -EIO;
>  	}
>  
> @@ -838,12 +842,14 @@ 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_inbuf);
>  	kfree(pneg_rsp);
>  	return 0;
>  
>  vneg_out:
>  	cifs_dbg(VFS, "protocol revalidation - security settings mismatch\n");
>  err_rsp_free:
> +	kfree(pneg_inbuf);
>  	kfree(pneg_rsp);
>  	return -EIO;
>  }
> -- 
> 2.7.4

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>