Re: [PATCH] cifs: move some variables off the stack in smb2_ioctl_query_info

[Steve French <smfrench@gmail.com>]

tentatively merged this and the previous patch into for-next pending
more testing

On Thu, May 21, 2020 at 12:03 AM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> Move some large data structures off the stack and into dynamically
> allocated memory in the function smb2_ioctl_query_info
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/smb2ops.c | 58 +++++++++++++++++++++++++++++++++----------------------
>  1 file changed, 35 insertions(+), 23 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index f829f4165d38..fa5c79f64c0b 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -1452,6 +1452,16 @@ SMB2_request_res_key(const unsigned int xid, struct cifs_tcon *tcon,
>         return rc;
>  }
>
> +struct iqi_vars {
> +       struct smb_rqst rqst[3];
> +       struct kvec rsp_iov[3];
> +       struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
> +       struct kvec qi_iov[1];
> +       struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
> +       struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
> +       struct kvec close_iov[1];
> +};
> +
>  static int
>  smb2_ioctl_query_info(const unsigned int xid,
>                       struct cifs_tcon *tcon,
> @@ -1459,6 +1469,9 @@ smb2_ioctl_query_info(const unsigned int xid,
>                       __le16 *path, int is_dir,
>                       unsigned long p)
>  {
> +       struct iqi_vars *vars;
> +       struct smb_rqst *rqst;
> +       struct kvec *rsp_iov;
>         struct cifs_ses *ses = tcon->ses;
>         char __user *arg = (char __user *)p;
>         struct smb_query_info qi;
> @@ -1468,45 +1481,47 @@ smb2_ioctl_query_info(const unsigned int xid,
>         struct smb2_query_info_rsp *qi_rsp = NULL;
>         struct smb2_ioctl_rsp *io_rsp = NULL;
>         void *buffer = NULL;
> -       struct smb_rqst rqst[3];
>         int resp_buftype[3];
> -       struct kvec rsp_iov[3];
> -       struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
>         struct cifs_open_parms oparms;
>         u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
>         struct cifs_fid fid;
> -       struct kvec qi_iov[1];
> -       struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
> -       struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
> -       struct kvec close_iov[1];
>         unsigned int size[2];
>         void *data[2];
>         int create_options = is_dir ? CREATE_NOT_FILE : CREATE_NOT_DIR;
>
> -       memset(rqst, 0, sizeof(rqst));
> +       vars = kzalloc(sizeof(*vars), GFP_ATOMIC);
> +       if (vars == NULL)
> +               return -ENOMEM;
> +       rqst = &vars->rqst[0];
> +       rsp_iov = &vars->rsp_iov[0];
> +
>         resp_buftype[0] = resp_buftype[1] = resp_buftype[2] = CIFS_NO_BUFFER;
> -       memset(rsp_iov, 0, sizeof(rsp_iov));
>
>         if (copy_from_user(&qi, arg, sizeof(struct smb_query_info)))
> -               return -EFAULT;
> +               goto e_fault;
>
> -       if (qi.output_buffer_length > 1024)
> +       if (qi.output_buffer_length > 1024) {
> +               kfree(vars);
>                 return -EINVAL;
> +       }
>
> -       if (!ses || !(ses->server))
> +       if (!ses || !(ses->server)) {
> +               kfree(vars);
>                 return -EIO;
> +       }
>
>         if (smb3_encryption_required(tcon))
>                 flags |= CIFS_TRANSFORM_REQ;
>
>         buffer = memdup_user(arg + sizeof(struct smb_query_info),
>                              qi.output_buffer_length);
> -       if (IS_ERR(buffer))
> +       if (IS_ERR(buffer)) {
> +               kfree(vars);
>                 return PTR_ERR(buffer);
> +       }
>
>         /* Open */
> -       memset(&open_iov, 0, sizeof(open_iov));
> -       rqst[0].rq_iov = open_iov;
> +       rqst[0].rq_iov = &vars->open_iov[0];
>         rqst[0].rq_nvec = SMB2_CREATE_IOV_SIZE;
>
>         memset(&oparms, 0, sizeof(oparms));
> @@ -1548,8 +1563,7 @@ smb2_ioctl_query_info(const unsigned int xid,
>                 if (!capable(CAP_SYS_ADMIN))
>                         rc = -EPERM;
>                 else  {
> -                       memset(&io_iov, 0, sizeof(io_iov));
> -                       rqst[1].rq_iov = io_iov;
> +                       rqst[1].rq_iov = &vars->io_iov[0];
>                         rqst[1].rq_nvec = SMB2_IOCTL_IOV_SIZE;
>
>                         rc = SMB2_ioctl_init(tcon, &rqst[1],
> @@ -1565,8 +1579,7 @@ smb2_ioctl_query_info(const unsigned int xid,
>                 if (!capable(CAP_SYS_ADMIN))
>                         rc = -EPERM;
>                 else  {
> -                       memset(&si_iov, 0, sizeof(si_iov));
> -                       rqst[1].rq_iov = si_iov;
> +                       rqst[1].rq_iov = &vars->si_iov[0];
>                         rqst[1].rq_nvec = 1;
>
>                         size[0] = 8;
> @@ -1579,8 +1592,7 @@ smb2_ioctl_query_info(const unsigned int xid,
>                                         SMB2_O_INFO_FILE, 0, data, size);
>                 }
>         } else if (qi.flags == PASSTHRU_QUERY_INFO) {
> -               memset(&qi_iov, 0, sizeof(qi_iov));
> -               rqst[1].rq_iov = qi_iov;
> +               rqst[1].rq_iov = &vars->qi_iov[0];
>                 rqst[1].rq_nvec = 1;
>
>                 rc = SMB2_query_info_init(tcon, &rqst[1], COMPOUND_FID,
> @@ -1599,8 +1611,7 @@ smb2_ioctl_query_info(const unsigned int xid,
>         smb2_set_related(&rqst[1]);
>
>         /* Close */
> -       memset(&close_iov, 0, sizeof(close_iov));
> -       rqst[2].rq_iov = close_iov;
> +       rqst[2].rq_iov = &vars->close_iov[0];
>         rqst[2].rq_nvec = 1;
>
>         rc = SMB2_close_init(tcon, &rqst[2], COMPOUND_FID, COMPOUND_FID, false);
> @@ -1649,6 +1660,7 @@ smb2_ioctl_query_info(const unsigned int xid,
>         }
>
>   iqinf_exit:
> +       kfree(vars);
>         kfree(buffer);
>         SMB2_open_free(&rqst[0]);
>         if (qi.flags & PASSTHRU_FSCTL)
> --
> 2.13.6
>


-- 
Thanks,

Steve