Messages in this thread | | | Date | Mon, 1 Apr 2024 14:18:25 -0500 | Subject | Re: [PATCH V2] x86/resctrl: Fix uninitialized memory read when last CPU of domain goes offline | From | "Moger, Babu" <> |
| |
On 4/1/24 13:16, Reinette Chatre wrote: > Tony encountered the OOPS below when the last CPU of a domain goes > offline while running a kernel built with CONFIG_NO_HZ_FULL: > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 > Oops: 0000 [#1] PREEMPT SMP NOPTI > ... > RIP: 0010:__find_nth_andnot_bit+0x66/0x110 > ... > Call Trace: > <TASK> > ? __die+0x1f/0x60 > ? page_fault_oops+0x176/0x5a0 > ? exc_page_fault+0x7f/0x260 > ? asm_exc_page_fault+0x22/0x30 > ? __pfx_resctrl_arch_offline_cpu+0x10/0x10 > ? __find_nth_andnot_bit+0x66/0x110 > ? __cancel_work+0x7d/0xc0 > cpumask_any_housekeeping+0x55/0x110 > mbm_setup_overflow_handler+0x40/0x70 > resctrl_offline_cpu+0x101/0x110 > resctrl_arch_offline_cpu+0x19/0x260 > cpuhp_invoke_callback+0x156/0x6b0 > ? cpuhp_thread_fun+0x5f/0x250 > cpuhp_thread_fun+0x1ca/0x250 > ? __pfx_smpboot_thread_fn+0x10/0x10 > smpboot_thread_fn+0x184/0x220 > kthread+0xe0/0x110 > ? __pfx_kthread+0x10/0x10 > ret_from_fork+0x2d/0x50 > ? __pfx_kthread+0x10/0x10 > ret_from_fork_asm+0x1a/0x30 > </TASK> > > The NULL pointer dereference is encountered while searching for another > online CPU in the domain (of which there are none) that can be used to > run the MBM overflow handler. > > Because the kernel is configured with CONFIG_NO_HZ_FULL the search for > another CPU (in its effort to prefer those CPUs that aren't marked > nohz_full) consults the mask representing the nohz_full CPUs, > tick_nohz_full_mask. On a kernel with CONFIG_CPUMASK_OFFSTACK=y > tick_nohz_full_mask is not allocated unless the kernel is booted with > the "nohz_full=" parameter and because of that any access to > tick_nohz_full_mask needs to be guarded with tick_nohz_full_enabled(). > > Replace the IS_ENABLED(CONFIG_NO_HZ_FULL) with tick_nohz_full_enabled(). > The latter ensures tick_nohz_full_mask can be accessed safely and can be > used whether kernel is built with CONFIG_NO_HZ_FULL enabled or not. > > Fixes: a4846aaf3945 ("x86/resctrl: Add cpumask_any_housekeeping() for limbo/overflow") > Reported-by: Tony Luck <tony.luck@intel.com> > Closes: https://lore.kernel.org/lkml/ZgIFT5gZgIQ9A9G7@agluck-desk3/ > Suggested-by: Ingo Molnar <mingo@kernel.org> > Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
-- Thanks Babu Moger
| |