On 3/11/2021 9:52 PM, Stefano Garzarella wrote:
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: [email protected] Cc: [email protected] Signed-off-by: Stefano Garzarella <[email protected]> --- drivers/vhost/vdpa.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index ef688c8c0e0e..00796e4ecfdf 100644 --- a/drivers/vhost/vdpa.c +++ b/drivers/vhost/vdpa.c @@ -308,8 +308,10 @@ static long vhost_vdpa_get_vring_num(struct vhost_vdpa *v, u16 __user *argp)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)
Thanks Stefano! Reviewed-by: Zhu Lingshan <[email protected]>
