Re: KASAN: use-after-free Read in ucma_close (2)

[Jason Gunthorpe]

On Fri, Sep 11, 2020 at 12:16:40PM +0800, Hillf Danton wrote:
> Detect race destroying ctx in order to avoid UAF.
> 
> +++ b/drivers/infiniband/core/ucma.c
> @@ -625,6 +625,10 @@ static ssize_t ucma_destroy_id(struct uc
>  		return PTR_ERR(ctx);
>  
>  	mutex_lock(&ctx->file->mut);
> +	if (ctx->destroying == 1) {
> +		mutex_unlock(&ctx->file->mut);
> +		return -ENXIO;
> +	}
>  	ctx->destroying = 1;
>  	mutex_unlock(&ctx->file->mut);
>  
> @@ -1826,6 +1830,8 @@ static int ucma_close(struct inode *inod
>  
>  	mutex_lock(&file->mut);
>  	list_for_each_entry_safe(ctx, tmp, &file->ctx_list, list) {
> +		if (ctx->destroying == 1)
> +			continue;
>  		ctx->destroying = 1;
>  		mutex_unlock(&file->mut);
>  

ucma_destroy_id() is called from write() and ucma_close is release(),
so there is no way these can race?

Jason