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    SubjectRe: [PATCH 1/3] sysfs: Fix crash on empty group attributes array
    Rafael J. Wysocki wrote:
    > On Thu, Feb 22, 2024 at 9:40 PM Dan Williams <dan.j.williams@intel.com> wrote:
    > >
    > > It turns out that arch/x86/events/intel/core.c makes use of "empty"
    > > attributes.
    > >
    > > static struct attribute *empty_attrs;
    > >
    > > __init int intel_pmu_init(void)
    > > {
    > > struct attribute **extra_skl_attr = &empty_attrs;
    > > struct attribute **extra_attr = &empty_attrs;
    > > struct attribute **td_attr = &empty_attrs;
    > > struct attribute **mem_attr = &empty_attrs;
    > > struct attribute **tsx_attr = &empty_attrs;
    > > ...
    > >
    > > That breaks the assumption __first_visible() that expects that if
    > > grp->attrs is set then grp->attrs[0] must also be set and results in
    > > backtraces like:
    > >
    > > BUG: kernel NULL pointer dereference, address: 00rnel mode
    > > #PF: error_code(0x0000) - not-present ] PREEMPT SMP NOPTI
    > > CPU: 1 PID: 1 Comm: swapper/IP: 0010:exra_is_visible+0x14/0x20
    > > ? exc_page_fault+0x68/0x190
    > > internal_create_groups+0x42/0xa0
    > > pmu_dev_alloc+0xc0/0xe0
    > > perf_event_sysfs_init+0x580000000000 ]---
    > > RIP: 0010:exra_is_visible+0x14/0
    > >
    > > Check for non-empty attributes array before calling is_visible().
    > >
    > > Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
    > > Closes: https://github.com/thesofproject/linux/pull/4799#issuecomment-1958537212
    > > Fixes: 70317fd24b41 ("sysfs: Introduce a mechanism to hide static attribute_groups")
    >
    > This is not in the mainline, so linux-next I suppose?

    ..or at least it will be shortly. Greg notified that it is currently in
    driver-core-next:

    https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/commit/?h=driver-core-next&id=70317fd24b41

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