From: Stefano Garzarella sgarzare@redhat.com
commit f6bbf0010ba004f5e90c7aefdebc0ee4bd3283b9 upstream.
When the 'v->config_ctx' eventfd_ctx reference is released we didn't set it to NULL. So if the same character device (e.g. /dev/vhost-vdpa-0) is re-opened, the 'v->config_ctx' is invalid and calling again vhost_vdpa_config_put() causes use-after-free issues like the following refcount_t underflow:
refcount_t: underflow; use-after-free. WARNING: CPU: 2 PID: 872 at lib/refcount.c:28 refcount_warn_saturate+0xae/0xf0 RIP: 0010:refcount_warn_saturate+0xae/0xf0 Call Trace: eventfd_ctx_put+0x5b/0x70 vhost_vdpa_release+0xcd/0x150 [vhost_vdpa] __fput+0x8e/0x240 ____fput+0xe/0x10 task_work_run+0x66/0xa0 exit_to_user_mode_prepare+0x118/0x120 syscall_exit_to_user_mode+0x21/0x50 ? __x64_sys_close+0x12/0x40 do_syscall_64+0x45/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xae
Fixes: 776f395004d8 ("vhost_vdpa: Support config interrupt in vdpa") Cc: lingshan.zhu@intel.com Cc: stable@vger.kernel.org Signed-off-by: Stefano Garzarella sgarzare@redhat.com Link: https://lore.kernel.org/r/20210311135257.109460-2-sgarzare@redhat.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Reviewed-by: Zhu Lingshan lingshan.zhu@intel.com Acked-by: Jason Wang jasowang@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/vhost/vdpa.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -312,8 +312,10 @@ static long vhost_vdpa_get_vring_num(str
static void vhost_vdpa_config_put(struct vhost_vdpa *v) { - if (v->config_ctx) + if (v->config_ctx) { eventfd_ctx_put(v->config_ctx); + v->config_ctx = NULL; + } }
static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)