From cdc497c6925be745bc895355bd4674a17a4b2a8b Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 1 Aug 2019 17:54:07 +0100 Subject: virtiofsd: prevent FUSE_INIT/FUSE_DESTROY races 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 Reviewed-by: Masayoshi Mizuma Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/fuse_i.h | 1 + tools/virtiofsd/fuse_lowlevel.c | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+) (limited to 'tools') diff --git a/tools/virtiofsd/fuse_i.h b/tools/virtiofsd/fuse_i.h index a20854f..1447d86 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 dab6a31..79a4031 100644 --- a/tools/virtiofsd/fuse_lowlevel.c +++ b/tools/virtiofsd/fuse_lowlevel.c @@ -2428,6 +2428,19 @@ void fuse_session_process_buf_int(struct fuse_session *se, req->ctx.pid = in->pid; req->ch = ch; + /* + * 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; @@ -2485,10 +2498,13 @@ 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) \ @@ -2531,6 +2547,7 @@ 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) { @@ -2610,6 +2627,7 @@ 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(); -- cgit v1.1