linux-kernel - Re: [PATCH 2/2] cifs: Allocate memory for all iovs in smb2

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Date:   Thu, 16 May 2019 09:11:32 +1000
From:   ronnie sahlberg <ronniesahlberg@...il.com>
To:     Long Li <longli@...rosoft.com>
Cc:     Steve French <sfrench@...ba.org>,
        linux-cifs <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] cifs: Allocate memory for all iovs in smb2_ioctl

On Thu, May 16, 2019 at 7:10 AM <longli@...uxonhyperv.com> wrote:
>
> From: Long Li <longli@...rosoft.com>
>
> An IOCTL uses up to 2 iovs. The 1st iov is the command itself, the 2nd iov is
> optional data for that command. The 1st iov is always allocated on the heap
> but the 2nd iov may point to a variable on the stack. This will trigger an
> error when passing the 2nd iov for RDMA I/O.
>
> Fix this by allocating a buffer for the 2nd iov.
>
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>  fs/cifs/smb2pdu.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
> index 29f011d8d8e2..710ceb875161 100644
> --- a/fs/cifs/smb2pdu.c
> +++ b/fs/cifs/smb2pdu.c
> @@ -2538,11 +2538,25 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
>         struct kvec *iov = rqst->rq_iov;
>         unsigned int total_len;
>         int rc;
> +       char *in_data_buf;
>
>         rc = smb2_plain_req_init(SMB2_IOCTL, tcon, (void **) &req, &total_len);
>         if (rc)
>                 return rc;
>
> +       if (indatalen) {
> +               /*
> +                * indatalen is usually small at a couple of bytes max, so
> +                * just allocate through generic pool
> +                */
> +               in_data_buf = kmalloc(indatalen, GFP_NOFS);
> +               if (!in_data_buf) {
> +                       cifs_small_buf_release(req);
> +                       return -ENOMEM;
> +               }
> +               memcpy(in_data_buf, in_data, indatalen);
> +       }
> +
>         req->CtlCode = cpu_to_le32(opcode);
>         req->PersistentFileId = persistent_fid;
>         req->VolatileFileId = volatile_fid;
> @@ -2563,7 +2577,7 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
>                        cpu_to_le32(offsetof(struct smb2_ioctl_req, Buffer));
>                 rqst->rq_nvec = 2;
>                 iov[0].iov_len = total_len - 1;
> -               iov[1].iov_base = in_data;
> +               iov[1].iov_base = in_data_buf;
>                 iov[1].iov_len = indatalen;
>         } else {
>                 rqst->rq_nvec = 1;
> @@ -2605,8 +2619,11 @@ SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
>  void
>  SMB2_ioctl_free(struct smb_rqst *rqst)
>  {
> -       if (rqst && rqst->rq_iov)
> +       if (rqst && rqst->rq_iov) {
>                 cifs_small_buf_release(rqst->rq_iov[0].iov_base); /* request */
> +               if (rqst->rq_iov[1].iov_len)
> +                       kfree(rqst->rq_iov[1].iov_base);

You don't need the conditional. kfree(NULL) is safe,.

> +       }
>  }
>
>
> --
> 2.17.1
>

Reviewed-by: Ronnie sahlberg <lsahlber@...hat.com>