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[83.57.172.113]) by smtp.gmail.com with ESMTPSA id u8sm9749149wmm.15.2020.01.17.05.40.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jan 2020 05:40:52 -0800 (PST) Subject: Re: [PATCH 101/104] virtiofsd: prevent FUSE_INIT/FUSE_DESTROY races To: "Dr. David Alan Gilbert (git)" , qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-102-dgilbert@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <73aa1b6c-612e-363e-dd49-04d1ba4f88f8@redhat.com> Date: Fri, 17 Jan 2020 14:40:51 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <20191212163904.159893-102-dgilbert@redhat.com> Content-Language: en-US X-MC-Unique: __kkDFV-MRyedEsBaPCCQQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/12/19 5:39 PM, Dr. David Alan Gilbert (git) wrote: > From: Stefan Hajnoczi > > 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 > --- > 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 typo "FUSE_INIT and FUSE_INIT" -> "FUSE_INIT and CUSE_INIT"? > + * 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(); >