On 18.11.2021 03:37, Stefano Stabellini wrote:
On Wed, 17 Nov 2021, Jan Beulich wrote:
On 17.11.2021 03:11, Stefano Stabellini wrote:
--- a/drivers/xen/xenbus/xenbus_probe.c +++ b/drivers/xen/xenbus/xenbus_probe.c @@ -951,6 +951,18 @@ static int __init xenbus_init(void) err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v); if (err) goto out_error;
/** Uninitialized hvm_params are zero and return no error.* Although it is theoretically possible to have* HVM_PARAM_STORE_PFN set to zero on purpose, in reality it is* not zero when valid. If zero, it means that Xenstore hasn't* been properly initialized. Instead of attempting to map a* wrong guest physical address return error.*/if (v == 0) {err = -ENOENT;goto out_error;}If such a check gets added, then I think known-invalid frame numbers should be covered at even higher a priority than zero.
Uhm, that's a good point. We could check for 0 and also ULONG_MAX
Why ULONG_MAX? The upper bound is determined by the number of physical address bits (in a guest: the virtual counterpart thereof). In a 32-bit environment ULONG_MAX could in principle even represent a valid frame number.
Jan