Messages in this thread | | | Date | Tue, 6 Sep 2022 22:38:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] perf: Allow restricted kernel breakpoints on user addresses |
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On Fri, Sep 02, 2022 at 12:00:57PM +0200, Marco Elver wrote: > Allow the creation of restricted breakpoint perf events that also fire > in the kernel (!exclude_kernel), if: > > 1. No sample information is requested; samples may contain IPs, > registers, or other information that may disclose kernel addresses. > > 2. The breakpoint (viz. data watchpoint) is on a user address. > > The rules constrain the allowable perf events such that no sensitive > kernel information can be disclosed. > > Despite no explicit kernel information disclosure, the following > questions may need answers: > > 1. Is obtaining information that the kernel accessed a particular > user's known memory location revealing new information? > Given the kernel's user space ABI, there should be no "surprise > accesses" to user space memory in the first place. > > 2. Does causing breakpoints on user memory accesses by the kernel > potentially impact timing in a sensitive way? > Since hardware breakpoints trigger regardless of the state of > perf_event_attr::exclude_kernel, but are filtered in the perf > subsystem, this possibility already exists independent of the > proposed change. >
Changelog forgot to tell us why you want this :-)
I don't see any immediate concerns, but it's late so who knows..
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