* Masayoshi Mizuma (msys.miz...@gmail.com) wrote:
> On Thu, Dec 12, 2019 at 04:39:01PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: Stefan Hajnoczi <stefa...@redhat.com>
> >
> > 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>
> > ---
> > tools/virtiofsd/fuse_i.h | 1 +
> > tools/virtiofsd/fuse_lowlevel.c | 18 ++++++++++++++++++
> > 2 files changed, 19 insertions(+)
> >
> > diff --git a/tools/virtiofsd/fuse_i.h b/tools/virtiofsd/fuse_i.h
> > index d0679508cd..8a4a05b319 100644
> > --- a/tools/virtiofsd/fuse_i.h
> > +++ b/tools/virtiofsd/fuse_i.h
> > @@ -61,6 +61,7 @@ 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/tools/virtiofsd/fuse_lowlevel.c
> > b/tools/virtiofsd/fuse_lowlevel.c
> > index 10f478b00c..9f01c05e3e 100644
> > --- a/tools/virtiofsd/fuse_lowlevel.c
> > +++ b/tools/virtiofsd/fuse_lowlevel.c
> > @@ -2431,6 +2431,19 @@ 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;
> > @@ -2488,10 +2501,13 @@ void fuse_session_process_buf_int(struct
> > fuse_session *se,
> > } 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) \
> > @@ -2538,6 +2554,7 @@ void fuse_session_destroy(struct fuse_session *se)
> > se->op.destroy(se->userdata);
> > }
> > }
> > + pthread_rwlock_destroy(&se->init_rwlock);
> > pthread_mutex_destroy(&se->lock);
> > free(se->cuse_data);
> > if (se->fd != -1) {
> > @@ -2631,6 +2648,7 @@ 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();
>
> Looks good to me.
>
> Reviewed-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>
Thanks
> > --
> > 2.23.0
> >
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
