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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 16 Sep 2016 00:22:11 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 3/3] 9pfs: handle walk of ".." in the
 root directory
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To: Greg Kurz <groug@kaod.org>, qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>, Felix Wilhelm <fwilhelm@ernw.de>, "Michael S. Tsirkin" <mst@redhat.com>, P J P <ppandit@redhat.com>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>



On 30/08/2016 20:40, Greg Kurz wrote:
> +
> +    err = fid_to_qid(pdu, fidp, &qid);
> +    if (err < 0) {
> +        goto out;
> +    }
> +
>      v9fs_path_init(&dpath);
>      v9fs_path_init(&path);

The "out" label can now be reached without having initialized dpath and
path.  This upsets Coverity (and might also cause a segfault, indeed).

The simplest fix is to move the v9fs_path_init before the fid_to_qid call.

Paolo

>      /*
> @@ -1318,16 +1334,22 @@ static void v9fs_walk(void *opaque)
>      v9fs_path_copy(&dpath, &fidp->path);
>      v9fs_path_copy(&path, &fidp->path);
>      for (name_idx = 0; name_idx < nwnames; name_idx++) {
> -        err = v9fs_co_name_to_path(pdu, &dpath, wnames[name_idx].data, &path);
> -        if (err < 0) {
> -            goto out;
> -        }
> -        err = v9fs_co_lstat(pdu, &path, &stbuf);
> -        if (err < 0) {
> -            goto out;
> +        if (not_same_qid(&pdu->s->root_qid, &qid) ||
> +            strcmp("..", wnames[name_idx].data)) {
> +            err = v9fs_co_name_to_path(pdu, &dpath, wnames[name_idx].data,
> +                                       &path);
> +            if (err < 0) {
> +                goto out;
> +            }
> +
> +            err = v9fs_co_lstat(pdu, &path, &stbuf);
> +            if (err < 0) {
> +                goto out;
> +            }
> +            stat_to_qid(&stbuf, &qid);
> +            v9fs_path_copy(&dpath, &path);
>          }
> -        stat_to_qid(&stbuf, &qids[name_idx]);
> -        v9fs_path_copy(&dpath, &path);
> +        memcpy(&qids[name_idx], &qid, sizeof(qid));
>      }
>      if (fid == newfid) {
>          BUG_ON(fidp->fid_type != P9_FID_NONE);
> diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
> index b4f757ab5449..a38603398ef5 100644
> --- a/hw/9pfs/9p.h
> +++ b/hw/9pfs/9p.h
> @@ -236,6 +236,7 @@ typedef struct V9fsState
>      int32_t root_fid;
>      Error *migration_blocker;
>      V9fsConf fsconf;
> +    V9fsQID root_qid;
>  } V9fsState;
>  
>  /* 9p2000.L open flags */
> 
> 
>