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

[Long Li]

> Subject: RE: [PATCH 2/6] cifs: Allocate validate negoation request through
> kmalloc
> 
> 
> 
> > -----Original Message-----
> > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Long Li
> > Sent: Monday, April 16, 2018 7:49 PM
> > To: Steve French <sfrench@xxxxxxxxx>; linux-cifs@xxxxxxxxxxxxxxx;
> > samba- technical@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> > rdma@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx
> > Cc: longli <longli@xxxxxxxxxxxxx>
> > Subject: [PATCH 2/6] cifs: Allocate validate negoation 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.
> >
> Please provide Fixes ("12-letters commit id") "commit string" which
> introduced this issue and it is getting fixed here, so that other can apply this
> fix to older versions.

Will do.

> 
> > Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> > ---
> >  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;
> [..]
> 
> >  	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;
> Instead of duplicating code here, please jump to err_rsp_free label. Kfree()
> takes care to not panic for NULL pointer.
> Or for clarity define new label.

I will fix this.

> 
> >  	}
> >
> > @@ -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
> >
> > --
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