diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9a37035..4d7bcbb 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2015,7 +2015,7 @@ int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
 	if (ctx->flags & IORING_SETUP_SQ_REWIND)
 		entries = ctx->sq_entries;
 	else
-		entries = io_sqring_entries(ctx);
+		entries = __io_sqring_entries(ctx);
 
 	entries = min(nr, entries);
 	if (unlikely(!entries))
@@ -2250,7 +2250,9 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	 */
 	poll_wait(file, &ctx->poll_wq, wait);
 
-	if (!io_sqring_full(ctx))
+	rcu_read_lock();
+
+	if (!__io_sqring_full(ctx))
 		mask |= EPOLLOUT | EPOLLWRNORM;
 
 	/*
@@ -2270,6 +2272,7 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
 	if (__io_cqring_events_user(ctx) || io_has_work(ctx))
 		mask |= EPOLLIN | EPOLLRDNORM;
 
+	rcu_read_unlock();
 	return mask;
 }
 
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 0fa844f..ee24bc5 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -142,16 +142,28 @@ struct io_wait_queue {
 #endif
 };
 
+static inline struct io_rings *io_get_rings(struct io_ring_ctx *ctx)
+{
+	return rcu_dereference_check(ctx->rings_rcu,
+			lockdep_is_held(&ctx->uring_lock) ||
+			lockdep_is_held(&ctx->completion_lock));
+}
+
 static inline bool io_should_wake(struct io_wait_queue *iowq)
 {
 	struct io_ring_ctx *ctx = iowq->ctx;
-	int dist = READ_ONCE(ctx->rings->cq.tail) - (int) iowq->cq_tail;
+	struct io_rings *rings;
+	int dist;
+
+	guard(rcu)();
+	rings = io_get_rings(ctx);
 
 	/*
 	 * Wake up if we have enough events, or if a timeout occurred since we
 	 * started waiting. For timeouts, we always want to return to userspace,
 	 * regardless of event count.
 	 */
+	dist = READ_ONCE(rings->cq.tail) - (int) iowq->cq_tail;
 	return dist >= 0 || atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts;
 }
 
@@ -431,9 +443,9 @@ static inline void io_cqring_wake(struct io_ring_ctx *ctx)
 	__io_wq_wake(&ctx->cq_wait);
 }
 
-static inline bool io_sqring_full(struct io_ring_ctx *ctx)
+static inline bool __io_sqring_full(struct io_ring_ctx *ctx)
 {
-	struct io_rings *r = ctx->rings;
+	struct io_rings *r = io_get_rings(ctx);
 
 	/*
 	 * SQPOLL must use the actual sqring head, as using the cached_sq_head
@@ -445,9 +457,15 @@ static inline bool io_sqring_full(struct io_ring_ctx *ctx)
 	return READ_ONCE(r->sq.tail) - READ_ONCE(r->sq.head) == ctx->sq_entries;
 }
 
-static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
+static inline bool io_sqring_full(struct io_ring_ctx *ctx)
 {
-	struct io_rings *rings = ctx->rings;
+	guard(rcu)();
+	return __io_sqring_full(ctx);
+}
+
+static inline unsigned int __io_sqring_entries(struct io_ring_ctx *ctx)
+{
+	struct io_rings *rings = io_get_rings(ctx);
 	unsigned int entries;
 
 	/* make sure SQ entry isn't read before tail */
@@ -455,6 +473,12 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
 	return min(entries, ctx->sq_entries);
 }
 
+static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
+{
+	guard(rcu)();
+	return __io_sqring_entries(ctx);
+}
+
 /*
  * Don't complete immediately but use deferred completion infrastructure.
  * Protected by ->uring_lock and can only be used either with
diff --git a/io_uring/net.c b/io_uring/net.c
index d27adbe..8885d94 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -421,6 +421,8 @@ int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	sr->done_io = 0;
 	sr->len = READ_ONCE(sqe->len);
+	if (unlikely(sr->len < 0))
+		return -EINVAL;
 	sr->flags = READ_ONCE(sqe->ioprio);
 	if (sr->flags & ~SENDMSG_FLAGS)
 		return -EINVAL;
@@ -791,6 +793,8 @@ int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	sr->umsg = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	sr->len = READ_ONCE(sqe->len);
+	if (unlikely(sr->len < 0))
+		return -EINVAL;
 	sr->flags = READ_ONCE(sqe->ioprio);
 	if (sr->flags & ~RECVMSG_FLAGS)
 		return -EINVAL;
diff --git a/io_uring/register.c b/io_uring/register.c
index 0148735..05362fe 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -178,9 +178,17 @@ static __cold int io_register_restrictions(struct io_ring_ctx *ctx,
 		return -EBUSY;
 
 	ret = io_parse_restrictions(arg, nr_args, &ctx->restrictions);
-	/* Reset all restrictions if an error happened */
+	/*
+	 * Reset all restrictions if an error happened, but retain any COW'ed
+	 * settings.
+	 */
 	if (ret < 0) {
+		struct io_bpf_filters *bpf = ctx->restrictions.bpf_filters;
+		bool cowed = ctx->restrictions.bpf_filters_cow;
+
 		memset(&ctx->restrictions, 0, sizeof(ctx->restrictions));
+		ctx->restrictions.bpf_filters = bpf;
+		ctx->restrictions.bpf_filters_cow = cowed;
 		return ret;
 	}
 	if (ctx->restrictions.op_registered)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 4fa59bf..1b96ab5 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1061,6 +1061,10 @@ static int io_import_fixed(int ddir, struct iov_iter *iter,
 		return ret;
 	if (!(imu->dir & (1 << ddir)))
 		return -EFAULT;
+	if (unlikely(!len)) {
+		iov_iter_bvec(iter, ddir, NULL, 0, 0);
+		return 0;
+	}
 
 	offset = buf_addr - imu->ubuf;
 
diff --git a/io_uring/wait.c b/io_uring/wait.c
index 0581cad..91df86c 100644
--- a/io_uring/wait.c
+++ b/io_uring/wait.c
@@ -79,12 +79,15 @@ static enum hrtimer_restart io_cqring_min_timer_wakeup(struct hrtimer *timer)
 	if (io_has_work(ctx))
 		goto out_wake;
 	/* got events since we started waiting, min timeout is done */
-	if (iowq->cq_min_tail != READ_ONCE(ctx->rings->cq.tail))
-		goto out_wake;
-	/* if we have any events and min timeout expired, we're done */
-	if (io_cqring_events(ctx))
-		goto out_wake;
+	scoped_guard(rcu) {
+		struct io_rings *rings = io_get_rings(ctx);
 
+		if (iowq->cq_min_tail != READ_ONCE(rings->cq.tail))
+			goto out_wake;
+		/* if we have any events and min timeout expired, we're done */
+		if (io_cqring_events(ctx))
+			goto out_wake;
+	}
 	/*
 	 * If using deferred task_work running and application is waiting on
 	 * more than one request, ensure we reset it now where we are switching
@@ -186,9 +189,9 @@ int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
 		   struct ext_arg *ext_arg)
 {
 	struct io_wait_queue iowq;
-	struct io_rings *rings = ctx->rings;
+	struct io_rings *rings;
 	ktime_t start_time;
-	int ret;
+	int ret, nr_wait;
 
 	min_events = min_t(int, min_events, ctx->cq_entries);
 
@@ -201,15 +204,23 @@ int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
 
 	if (unlikely(test_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq)))
 		io_cqring_do_overflow_flush(ctx);
-	if (__io_cqring_events_user(ctx) >= min_events)
+
+	rcu_read_lock();
+	rings = io_get_rings(ctx);
+	if (__io_cqring_events_user(ctx) >= min_events) {
+		rcu_read_unlock();
 		return 0;
+	}
 
 	init_waitqueue_func_entry(&iowq.wq, io_wake_function);
 	iowq.wq.private = current;
 	INIT_LIST_HEAD(&iowq.wq.entry);
 	iowq.ctx = ctx;
-	iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;
-	iowq.cq_min_tail = READ_ONCE(ctx->rings->cq.tail);
+	iowq.cq_tail = READ_ONCE(rings->cq.head) + min_events;
+	iowq.cq_min_tail = READ_ONCE(rings->cq.tail);
+	nr_wait = (int) iowq.cq_tail - READ_ONCE(rings->cq.tail);
+	rcu_read_unlock();
+	rings = NULL;
 	iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
 	iowq.hit_timeout = 0;
 	iowq.min_timeout = ext_arg->min_time;
@@ -240,14 +251,6 @@ int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
 	trace_io_uring_cqring_wait(ctx, min_events);
 	do {
 		unsigned long check_cq;
-		int nr_wait;
-
-		/* if min timeout has been hit, don't reset wait count */
-		if (!iowq.hit_timeout)
-			nr_wait = (int) iowq.cq_tail -
-					READ_ONCE(ctx->rings->cq.tail);
-		else
-			nr_wait = 1;
 
 		if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) {
 			atomic_set(&ctx->cq_wait_nr, nr_wait);
@@ -298,11 +301,20 @@ int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags,
 			break;
 		}
 		cond_resched();
+
+		/* if min timeout has been hit, don't reset wait count */
+		if (!iowq.hit_timeout)
+			scoped_guard(rcu)
+				nr_wait = (int) iowq.cq_tail -
+						READ_ONCE(io_get_rings(ctx)->cq.tail);
+		else
+			nr_wait = 1;
 	} while (1);
 
 	if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
 		finish_wait(&ctx->cq_wait, &iowq.wq);
 	restore_saved_sigmask_unless(ret == -EINTR);
 
-	return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
+	guard(rcu)();
+	return READ_ONCE(io_get_rings(ctx)->cq.head) == READ_ONCE(io_get_rings(ctx)->cq.tail) ? ret : 0;
 }
diff --git a/io_uring/wait.h b/io_uring/wait.h
index 5e236f7..3a145fc 100644
--- a/io_uring/wait.h
+++ b/io_uring/wait.h
@@ -28,12 +28,15 @@ void io_cqring_do_overflow_flush(struct io_ring_ctx *ctx);
 
 static inline unsigned int __io_cqring_events(struct io_ring_ctx *ctx)
 {
-	return ctx->cached_cq_tail - READ_ONCE(ctx->rings->cq.head);
+	struct io_rings *rings = io_get_rings(ctx);
+	return ctx->cached_cq_tail - READ_ONCE(rings->cq.head);
 }
 
 static inline unsigned int __io_cqring_events_user(struct io_ring_ctx *ctx)
 {
-	return READ_ONCE(ctx->rings->cq.tail) - READ_ONCE(ctx->rings->cq.head);
+	struct io_rings *rings = io_get_rings(ctx);
+
+	return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head);
 }
 
 /*