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X-Proofpoint-GUID: pG6zQBwjiMDilIhf8ioJgAKbjg1Jj0zY X-Proofpoint-ORIG-GUID: pG6zQBwjiMDilIhf8ioJgAKbjg1Jj0zY On Tue, Aug 12, 2025 at 12:06:13PM +0200, Peter Zijlstra wrote: > On Mon, Aug 11, 2025 at 02:21:08PM +0100, Lorenzo Stoakes wrote: > > Reviewed-by: Lorenzo Stoakes > > Well, there's still that problem below. That was a goto unlock and would > pass through the perf_mmap_account() and atomic_inc(mmap_count), where > now it does not. Yep, you're right, damn it. I managed to miss this one among all the rest, and I was looking very very carefully bit-by-bit... goes to show just how horrible the code was in teh first place. > > Arguably it should not do the perf_mmap_account(), but lets keep the > code functionally equivalent for now. > > Anyway, I've re-done these two break-out patches in a more fine grained > fashion and will post a new series in a few. OK will take a look. > > > > --- > > > V2: Fixup invers condition and add the dropped flags setup back - Lorenzo > > > Fixup subject line to match the content > > > --- > > > kernel/events/core.c | 137 +++++++++++++++++++++++++++++---------------------- > > > 1 file changed, 78 insertions(+), 59 deletions(-) > > > > > > --- a/kernel/events/core.c > > > +++ b/kernel/events/core.c > > > @@ -6970,12 +6970,79 @@ static void perf_mmap_account(struct vm_ > > > atomic64_add(extra, &vma->vm_mm->pinned_vm); > > > } > > > > > > +static int perf_mmap_aux(struct vm_area_struct *vma, struct perf_event *event, > > > + unsigned long nr_pages) > > > +{ > > > + long user_extra = nr_pages, extra = 0; > > > + struct perf_buffer *rb = event->rb; > > > + u64 aux_offset, aux_size; > > > + int ret, rb_flags = 0; > > > + > > > + /* > > > + * AUX area mapping: if rb->aux_nr_pages != 0, it's already > > > + * mapped, all subsequent mappings should have the same size > > > + * and offset. Must be above the normal perf buffer. > > > + */ > > > + aux_offset = READ_ONCE(rb->user_page->aux_offset); > > > + aux_size = READ_ONCE(rb->user_page->aux_size); > > > + > > > + if (aux_offset < perf_data_size(rb) + PAGE_SIZE) > > > + return -EINVAL; > > > + > > > + if (aux_offset != vma->vm_pgoff << PAGE_SHIFT) > > > + return -EINVAL; > > > + > > > + /* Already mapped with a different offset */ > > > + if (rb_has_aux(rb) && rb->aux_pgoff != vma->vm_pgoff) > > > + return -EINVAL; > > > + > > > + if (aux_size != nr_pages * PAGE_SIZE) > > > + return -EINVAL; > > > + > > > + /* Already mapped with a different size */ > > > + if (rb_has_aux(rb) && rb->aux_nr_pages != nr_pages) > > > + return -EINVAL; > > > + > > > + if (!is_power_of_2(nr_pages)) > > > + return -EINVAL; > > > + > > > + /* If this succeeds, subsequent failures have to undo it */ > > > + if (!atomic_inc_not_zero(&rb->mmap_count)) > > > + return -EINVAL; > > > + > > > + /* If mapped, attach to it */ > > > + if (rb_has_aux(rb)) { > > > + atomic_inc(&rb->aux_mmap_count); > > > + return 0; > > here, the return 0 should've been a goto to... Yeah... I think I had assumed we fixed this up somehow on the return but of course we can't since we moved the perf_map_account() here (nor could we differentiate return values). But I think partly a product of the diff not showing that bit and, despite checking line-by-line against old version I just about missed this one. Yeah, this code, this refactor is very much needed! > > > > + } > > > + > > > + if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) { > > > + atomic_dec(&rb->mmap_count); > > > + return -EPERM; > > > + } > > > + > > > + if (vma->vm_flags & VM_WRITE) > > > + rb_flags |= RING_BUFFER_WRITABLE; > > > + > > > + ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages, > > > + event->attr.aux_watermark, rb_flags); > > > + if (ret) { > > > + atomic_dec(&rb->mmap_count); > > > + return ret; > > > + } > > > + > > > + atomic_set(&rb->aux_mmap_count, 1); > > > + rb->aux_mmap_locked = extra; > > here: > > > > + perf_mmap_account(vma, user_extra, extra); > > > + atomic_inc(&event->mmap_count); > > > + return 0; > > > +}