Re: [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref
From: Sean Christopherson <seanjc@google.com>
Date: 2021-11-11 00:40:00
Also in:
kvm, kvmarm, linux-perf-users, linux-riscv, lkml, xen-devel
On Wed, Nov 10, 2021, Paolo Bonzini wrote:
On 11/4/21 15:18, Sean Christopherson wrote:quoted
If I'm interpeting Paolo's suggestion correctly, he's pointing out that oustanding stores to the function pointers in @cbs need to complete before assigning a non-NULL pointer to perf_guest_cbs, otherwise a perf event handler may see a valid pointer with half-baked callbacks. I think smp_store_release() with a comment would be appropriate, assuming my above interpretation is correct.Yes, exactly. It should even be rcu_assign_pointer(), matching the synchronize_rcu()
And perf_guest_cbs should be tagged __rcu and accessed accordingly. Which is
effectively what this version (poorly) implemented with a homebrewed mix of
{READ,WRITE}_ONCE, lockdep(), and synchronize_rcu().
in patch 1 (and the change can be done in patch 1, too).
Ya, the change needs to go into patch 1. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel