Fix a heap-use-after-free in the virtio-rng frontend when a delayed rng-random backend completion arrives after the virtio-rng device has been hot-unplugged.
Fixes: CVE-2026-50624 Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3917 Reported-by: Jia Jia <[email protected]> Signed-off-by: Laurent Vivier <[email protected]> --- backends/rng.c | 16 ++++++++++++++++ hw/virtio/virtio-rng.c | 2 ++ include/system/rng.h | 14 ++++++++++++++ 3 files changed, 32 insertions(+) diff --git a/backends/rng.c b/backends/rng.c index ab94dfea850a..182269be4a83 100644 --- a/backends/rng.c +++ b/backends/rng.c @@ -68,6 +68,22 @@ static void rng_backend_free_request(RngRequest *req) g_free(req); } +void rng_backend_cancel_request_entropy(RngBackend *s, + EntropyReceiveFunc *receive_entropy, + void *opaque) +{ + RngRequest *req, *next; + + QSIMPLEQ_FOREACH_SAFE(req, &s->requests, next, next) { + if (req->receive_entropy != receive_entropy || + req->opaque != opaque) { + continue; + } + QSIMPLEQ_REMOVE(&s->requests, req, RngRequest, next); + rng_backend_free_request(req); + } +} + static void rng_backend_free_requests(RngBackend *s) { RngRequest *req, *next; diff --git a/hw/virtio/virtio-rng.c b/hw/virtio/virtio-rng.c index 66690a34dc97..a77ea5ab1385 100644 --- a/hw/virtio/virtio-rng.c +++ b/hw/virtio/virtio-rng.c @@ -234,6 +234,8 @@ static void virtio_rng_device_unrealize(DeviceState *dev) VirtIODevice *vdev = VIRTIO_DEVICE(dev); VirtIORNG *vrng = VIRTIO_RNG(dev); + rng_backend_cancel_request_entropy(vrng->rng, chr_read, vrng); + qemu_del_vm_change_state_handler(vrng->vmstate); timer_free(vrng->rate_limit_timer); virtio_del_queue(vdev, 0); diff --git a/include/system/rng.h b/include/system/rng.h index e383f87d20b2..5b0893eb2bd5 100644 --- a/include/system/rng.h +++ b/include/system/rng.h @@ -86,4 +86,18 @@ void rng_backend_request_entropy(RngBackend *s, size_t size, * deleted. */ void rng_backend_finalize_request(RngBackend *s, RngRequest *req); + +/** + * rng_backend_cancel_request_entropy: + * @s: the backend that created the request + * @receive_entropy: the function invoked when entropy is available + * @opaque: data passed to @receive_entropy + * + * This function is used by the front-end to cancel all requests to a + * given backend. Requests to cancel are identified by the receive_entropy + * function and the data passed to the function. + */ +void rng_backend_cancel_request_entropy(RngBackend *s, + EntropyReceiveFunc *receive_entropy, + void *opaque); #endif -- 2.54.0
