RE: [Patch v2 2/6] cifs: Allocate validate negotiation request through kmalloc

[Parav Pandit]

> -----Original Message-----
> From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Long Li
> Sent: Tuesday, April 17, 2018 2:17 PM
> To: Steve French <sfrench@xxxxxxxxx>; linux-cifs@xxxxxxxxxxxxxxx; samba-
> technical@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> rdma@xxxxxxxxxxxxxxx
> Cc: longli <longli@xxxxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx
> Subject: [Patch v2 2/6] cifs: Allocate validate negotiation request through
> kmalloc
> 
> 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.
> 
> Fix this by allocating the request on the heap in smb3_validate_negotiate.
> 
> Fixes: ff1c038addc4f205d5f1ede449426c7d316c0eed "Check SMB3 dialects
> against downgrade attacks"
> 

Format is:
Fixes: ff1c038addc4 ("Check SMB3 dialects against downgrade attacks")
It should be right above Signed-off signature.

> Changes in v2:
> Removed duplicated code on freeing buffers on function exit.
> (Thanks to Parav Pandit <parav@xxxxxxxxxxxx>)
> 
> Fixed typo in the patch title.
> 
> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  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 = 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;
> 
>  	/* In SMB3.11 preauth integrity supersedes validate negotiate */
>  	if (tcon->ses->server->dialect == 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 =
> +	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,
Please check if strncmp() should be used or not.

>  		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(struct validate_negotiate_info_req),

Use sizeof(*pneg_inbuf)

>  		(char **)&pneg_rsp, &rsplen);
> 
> -	if (rc != 0) {
> -		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", rc);
> -		return -EIO;
> +	if (ret != 0) {

if (ret) is fine.

> +		cifs_dbg(VFS, "validate protocol negotiate failed: %d\n", ret);
> +		goto out_free_inbuf;
>  	}
> 
>  	if (rsplen != sizeof(struct validate_negotiate_info_rsp)) { @@ -820,7

if (rsplen != sizeof(*pneg_rsp))