CVE-2024-35929

In the Linux kernel, the following vulnerability has been resolved:
rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() For the kernels
built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and CONFIG_RCU_LAZY=y, the
following scenarios will trigger WARN_ON_ONCE() in the
rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions: CPU2 CPU11
kthread rcu_nocb_cb_kthread ksys_write rcu_do_batch vfs_write
rcu_torture_timer_cb proc_sys_write __kmem_cache_free proc_sys_call_handler
kmemleak_free drop_caches_sysctl_handler delete_object_full drop_slab
__delete_object shrink_slab put_object lazy_rcu_shrink_scan call_rcu
rcu_nocb_flush_bypass _call_rcu_commn rcu_nocb_bypass_lock
raw_spin_trylock(&rdp->nocb_bypass_lock) fail
atomic_inc(&rdp->nocb_lock_contended); rcu_nocb_wait_contended
WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) | | _ _ _ _ _ _ _ _
same rdp and rdp->cpu != 11 _ _ _ _ _ _ _ _ __| Reproduce this bug with
“echo 3 > /proc/sys/vm/drop_caches”. This commit therefore uses
rcu_nocb_try_flush_bypass() instead of rcu_nocb_flush_bypass() in
lazy_rcu_shrink_scan(). If the nocb_bypass queue is being flushed, then
rcu_nocb_try_flush_bypass will return directly.