* Stefan Hajnoczi (stefa...@redhat.com) wrote:
> When running with multiple threads it can be tricky to handle
> FUSE_INIT/FUSE_DESTROY in parallel with other request types or in
> parallel with themselves. Serialize FUSE_INIT and FUSE_DESTROY so that
> malicious clients cannot trigger race conditions.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
(It took me a few minutes getting my head around the different _destroy
functions)
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> contrib/virtiofsd/fuse_i.h | 1 +
> contrib/virtiofsd/fuse_lowlevel.c | 17 +++++++++++++++++
> 2 files changed, 18 insertions(+)
>
> diff --git a/contrib/virtiofsd/fuse_i.h b/contrib/virtiofsd/fuse_i.h
> index ff6e1b75ba..dcde9feb97 100644
> --- a/contrib/virtiofsd/fuse_i.h
> +++ b/contrib/virtiofsd/fuse_i.h
> @@ -63,6 +63,7 @@ struct fuse_session {
> struct fuse_req list;
> struct fuse_req interrupts;
> pthread_mutex_t lock;
> + pthread_rwlock_t init_rwlock;
> int got_destroy;
> int broken_splice_nonblock;
> uint64_t notify_ctr;
> diff --git a/contrib/virtiofsd/fuse_lowlevel.c
> b/contrib/virtiofsd/fuse_lowlevel.c
> index 6ebf237baa..483a1bc9be 100644
> --- a/contrib/virtiofsd/fuse_lowlevel.c
> +++ b/contrib/virtiofsd/fuse_lowlevel.c
> @@ -2473,6 +2473,18 @@ void fuse_session_process_buf_int(struct fuse_session
> *se,
> req->ctx.pid = in->pid;
> req->ch = ch ? fuse_chan_get(ch) : NULL;
>
> + /* INIT and DESTROY requests are serialized, all other request types
> + * run in parallel. This prevents races between FUSE_INIT and ordinary
> + * requests, FUSE_INIT and FUSE_INIT, FUSE_INIT and FUSE_DESTROY, and
> + * FUSE_DESTROY and FUSE_DESTROY.
> + */
> + if (in->opcode == FUSE_INIT || in->opcode == CUSE_INIT ||
> + in->opcode == FUSE_DESTROY) {
> + pthread_rwlock_wrlock(&se->init_rwlock);
> + } else {
> + pthread_rwlock_rdlock(&se->init_rwlock);
> + }
> +
> err = EIO;
> if (!se->got_init) {
> enum fuse_opcode expected;
> @@ -2524,10 +2536,13 @@ void fuse_session_process_buf_int(struct fuse_session
> *se,
> do_write_buf(req, in->nodeid, &iter, bufv);
> else
> fuse_ll_ops[in->opcode].func(req, in->nodeid, &iter);
> +
> + pthread_rwlock_unlock(&se->init_rwlock);
> return;
>
> reply_err:
> fuse_reply_err(req, err);
> + pthread_rwlock_unlock(&se->init_rwlock);
> }
>
> #define LL_OPTION(n,o,v) \
> @@ -2569,6 +2584,7 @@ void fuse_session_destroy(struct fuse_session *se)
> if (se->op.destroy)
> se->op.destroy(se->userdata, se);
> }
> + pthread_rwlock_destroy(&se->init_rwlock);
> pthread_mutex_destroy(&se->lock);
> free(se->cuse_data);
> if (se->fd != -1)
> @@ -2656,6 +2672,7 @@ struct fuse_session *fuse_session_new(struct fuse_args
> *args,
> list_init_req(&se->list);
> list_init_req(&se->interrupts);
> fuse_mutex_init(&se->lock);
> + pthread_rwlock_init(&se->init_rwlock, NULL);
>
> memcpy(&se->op, op, op_size);
> se->owner = getuid();
> --
> 2.21.0
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
