Re: [PATCH] perf/core: fast breakpoint modification via _IOC_MODIFY_BREAKPOINT.

[Andi Kleen]

> +static int _perf_event_modify_breakpoint(struct perf_event *bp,
> +					 struct perf_event_attr *attr)
> +{
> +	u64 old_addr = bp->attr.bp_addr;
> +	u64 old_len = bp->attr.bp_len;
> +	int old_type = bp->attr.bp_type;
> +	int err = 0;
> +
> +	_perf_event_disable(bp);
> +
> +	bp->attr.bp_addr = attr->bp_addr;
> +	bp->attr.bp_type = attr->bp_type;
> +	bp->attr.bp_len = attr->bp_len;

You don't check any of the other fields, so user space is free
to fill in junk. That means they can never be used for anything.
It would be better to check at least some of them for being
zero, and also that the type matches the break point.

-Andi