Dan Williams 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+0x14/0Check 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") Cc: Marc Herbert marc.herbert@intel.com
Ok, this one is now
Tested-by: Marc Herbert marc.herbert@intel.com
...per:
https://github.com/thesofproject/linux/pull/4799#issuecomment-1960469389
Thanks for all the help Marc!