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>
---
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
