From: Greg Kurz <groug@kaod.org>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: mszeredi@redhat.com, Daniel Berrange <berrange@redhat.com>,
slp@redhat.com, qemu-devel@nongnu.org,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
virtio-fs@redhat.com, P J P <ppandit@redhat.com>,
Laszlo Ersek <lersek@redhat.com>,
vgoyal@redhat.com
Subject: Re: [PATCH v4 2/3] virtiofsd: optionally return inode pointer from lo_do_lookup()
Date: Wed, 3 Feb 2021 15:20:14 +0100 [thread overview]
Message-ID: <20210203152014.443a8b29@bahia.lan> (raw)
In-Reply-To: <20210203113719.83633-3-stefanha@redhat.com>
On Wed, 3 Feb 2021 11:37:18 +0000
Stefan Hajnoczi <stefanha@redhat.com> wrote:
> lo_do_lookup() finds an existing inode or allocates a new one. It
> increments nlookup so that the inode stays alive until the client
> releases it.
>
> Existing callers don't need the struct lo_inode so the function doesn't
> return it. Extend the function to optionally return the inode. The next
> commit will need it.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> tools/virtiofsd/passthrough_ll.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index e63cbd3fb7..c87a1f3d72 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -831,11 +831,13 @@ static int do_statx(struct lo_data *lo, int dirfd, const char *pathname,
> }
>
> /*
> - * Increments nlookup and caller must release refcount using
> - * lo_inode_put(&parent).
> + * Increments nlookup on the inode on success. unref_inode_lolocked() must be
> + * called eventually to decrement nlookup again. If inodep is non-NULL, the
> + * inode pointer is stored and the caller must call lo_inode_put().
> */
> static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> - struct fuse_entry_param *e)
> + struct fuse_entry_param *e,
> + struct lo_inode **inodep)
> {
> int newfd;
> int res;
> @@ -845,6 +847,10 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> struct lo_inode *inode = NULL;
> struct lo_inode *dir = lo_inode(req, parent);
>
> + if (inodep) {
> + *inodep = NULL;
> + }
> +
Is this side-effect needed ? If lo_do_lookup() returns an error, it
rather seems that the caller shouldn't expect anything to be written
here, i.e. the content of *inodep still belongs to the caller and
whatever value it previously put in there (as patch 3/3 does) should
be preserved IMHO.
Apart from that LGTM.
> /*
> * name_to_handle_at() and open_by_handle_at() can reach here with fuse
> * mount point in guest, but we don't have its inode info in the
> @@ -913,7 +919,14 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
> pthread_mutex_unlock(&lo->mutex);
> }
> e->ino = inode->fuse_ino;
> - lo_inode_put(lo, &inode);
> +
> + /* Transfer ownership of inode pointer to caller or drop it */
> + if (inodep) {
> + *inodep = inode;
> + } else {
> + lo_inode_put(lo, &inode);
> + }
> +
> lo_inode_put(lo, &dir);
>
> fuse_log(FUSE_LOG_DEBUG, " %lli/%s -> %lli\n", (unsigned long long)parent,
> @@ -948,7 +961,7 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
> return;
> }
>
> - err = lo_do_lookup(req, parent, name, &e);
> + err = lo_do_lookup(req, parent, name, &e, NULL);
> if (err) {
> fuse_reply_err(req, err);
> } else {
> @@ -1056,7 +1069,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
> goto out;
> }
>
> - saverr = lo_do_lookup(req, parent, name, &e);
> + saverr = lo_do_lookup(req, parent, name, &e, NULL);
> if (saverr) {
> goto out;
> }
> @@ -1534,7 +1547,7 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size,
>
> if (plus) {
> if (!is_dot_or_dotdot(name)) {
> - err = lo_do_lookup(req, ino, name, &e);
> + err = lo_do_lookup(req, ino, name, &e, NULL);
> if (err) {
> goto error;
> }
> @@ -1732,7 +1745,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
> }
>
> fi->fh = fh;
> - err = lo_do_lookup(req, parent, name, &e);
> + err = lo_do_lookup(req, parent, name, &e, NULL);
> }
> if (lo->cache == CACHE_NONE) {
> fi->direct_io = 1;
next prev parent reply other threads:[~2021-02-03 14:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-03 11:37 [PATCH v4 0/3] virtiofsd: prevent opening of special files (CVE-2020-35517) Stefan Hajnoczi
2021-02-03 11:37 ` [PATCH v4 1/3] virtiofsd: extract lo_do_open() from lo_open() Stefan Hajnoczi
2021-02-03 14:20 ` Greg Kurz
2021-02-03 14:47 ` Dr. David Alan Gilbert
2021-02-03 15:45 ` Greg Kurz
2021-02-03 17:47 ` Greg Kurz
2021-02-03 16:57 ` Stefan Hajnoczi
2021-02-03 11:37 ` [PATCH v4 2/3] virtiofsd: optionally return inode pointer from lo_do_lookup() Stefan Hajnoczi
2021-02-03 14:20 ` Greg Kurz [this message]
2021-02-03 17:00 ` Stefan Hajnoczi
2021-02-04 8:25 ` Greg Kurz
2021-02-04 9:45 ` Stefan Hajnoczi
2021-02-04 11:19 ` Greg Kurz
2021-02-03 11:37 ` [PATCH v4 3/3] virtiofsd: prevent opening of special files (CVE-2020-35517) Stefan Hajnoczi
2021-02-03 15:28 ` Vivek Goyal
2021-02-03 16:02 ` Greg Kurz
2021-02-03 16:08 ` Vivek Goyal
2021-02-03 17:05 ` Stefan Hajnoczi
2021-02-03 18:05 ` Dr. David Alan Gilbert
2021-02-03 21:14 ` Vivek Goyal
2021-02-04 9:47 ` Stefan Hajnoczi
2021-02-03 15:57 ` Greg Kurz
2021-02-03 17:06 ` Stefan Hajnoczi
2021-02-03 11:46 ` [PATCH v4 0/3] " no-reply
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