On Thu 2022-06-09 14:33:19, Jason A. Donenfeld wrote: > The RNG uses vanilla spinlocks, not raw spinlocks, so kfence should pick > its random numbers before taking its raw spinlocks. This also has the > nice effect of doing less work inside the lock. It should fix a splat > that Geert saw with CONFIG_PROVE_RAW_LOCK_NESTING: > > dump_backtrace.part.0+0x98/0xc0 > show_stack+0x14/0x28 > dump_stack_lvl+0xac/0xec > dump_stack+0x14/0x2c > __lock_acquire+0x388/0x10a0 > lock_acquire+0x190/0x2c0 > _raw_spin_lock_irqsave+0x6c/0x94 > crng_make_state+0x148/0x1e4 > _get_random_bytes.part.0+0x4c/0xe8 > get_random_u32+0x4c/0x140 > __kfence_alloc+0x460/0x5c4 > kmem_cache_alloc_trace+0x194/0x1dc > __kthread_create_on_node+0x5c/0x1a8 > kthread_create_on_node+0x58/0x7c > printk_start_kthread.part.0+0x34/0xa8 > printk_activate_kthreads+0x4c/0x54 > do_one_initcall+0xec/0x278 > kernel_init_freeable+0x11c/0x214 > kernel_init+0x24/0x124 > ret_from_fork+0x10/0x20 > > Cc: John Ogness <john.ogness@xxxxxxxxxxxxx> > Cc: Alexander Potapenko <glider@xxxxxxxxxx> > Cc: Marco Elver <elver@xxxxxxxxxx> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Reported-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Reviewed-by: Petr Mladek <pmladek@xxxxxxxx> Thanks a lot for fixing this. It is great to know that the printk kthreads were not the culprit here ;-) Best Regards, Petr
