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();
--
2.23.0
