From e871abcda3b67d0820b4182ebe93435624e9c6a4 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 17 Apr 2024 13:38:29 +0200 Subject: random: handle creditable entropy from atomic process context The entropy accounting changes a static key when the RNG has initialized, since it only ever initializes once. Static key changes, however, cannot be made from atomic context, so depending on where the last creditable entropy comes from, the static key change might need to be deferred to a worker. Previously the code used the execute_in_process_context() helper function, which accounts for whether or not the caller is in_interrupt(). However, that doesn't account for the case where the caller is actually in process context but is holding a spinlock. This turned out to be the case with input_handle_event() in drivers/input/input.c contributing entropy: [] die+0xa8/0x2fc [] bug_handler+0x44/0xec [] brk_handler+0x90/0x144 [] do_debug_exception+0xa0/0x148 [] el1_dbg+0x60/0x7c [] el1h_64_sync_handler+0x38/0x90 [] el1h_64_sync+0x64/0x6c [] __might_resched+0x1fc/0x2e8 [] __might_sleep+0x44/0x7c [] cpus_read_lock+0x1c/0xec [] static_key_enable+0x14/0x38 [] crng_set_ready+0x14/0x28 [] execute_in_process_context+0xb8/0xf8 [] _credit_init_bits+0x118/0x1dc [] add_timer_randomness+0x264/0x270 [] add_input_randomness+0x38/0x48 [] input_handle_event+0x2b8/0x490 [] input_event+0x6c/0x98 According to Guoyong, it's not really possible to refactor the various drivers to never hold a spinlock there. And in_atomic() isn't reliable. So, rather than trying to be too fancy, just punt the change in the static key to a workqueue always. There's basically no drawback of doing this, as the code already needed to account for the static key not changing immediately, and given that it's just an optimization, there's not exactly a hurry to change the static key right away, so deferal is fine. Reported-by: Guoyong Wang Cc: stable@vger.kernel.org Fixes: f5bda35fba61 ("random: use static branch for crng_ready()") Signed-off-by: Jason A. Donenfeld --- drivers/char/random.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 456be28ba67cb..2597cb43f4387 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -702,7 +702,7 @@ static void extract_entropy(void *buf, size_t len) static void __cold _credit_init_bits(size_t bits) { - static struct execute_work set_ready; + static DECLARE_WORK(set_ready, crng_set_ready); unsigned int new, orig, add; unsigned long flags; @@ -718,8 +718,8 @@ static void __cold _credit_init_bits(size_t bits) if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) { crng_reseed(NULL); /* Sets crng_init to CRNG_READY under base_crng.lock. */ - if (static_key_initialized) - execute_in_process_context(crng_set_ready, &set_ready); + if (static_key_initialized && system_unbound_wq) + queue_work(system_unbound_wq, &set_ready); atomic_notifier_call_chain(&random_ready_notifier, 0, NULL); wake_up_interruptible(&crng_init_wait); kill_fasync(&fasync, SIGIO, POLL_IN); @@ -890,8 +890,8 @@ void __init random_init(void) /* * If we were initialized by the cpu or bootloader before jump labels - * are initialized, then we should enable the static branch here, where - * it's guaranteed that jump labels have been initialized. + * or workqueues are initialized, then we should enable the static + * branch here, where it's guaranteed that these have been initialized. */ if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY) crng_set_ready(NULL); -- cgit 1.2.3-korg From 3aadf100f93d80815685493d60cd8cab206403df Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Thu, 18 Apr 2024 13:45:17 +0200 Subject: Revert "vmgenid: emit uevent when VMGENID updates" This reverts commit ad6bcdad2b6724e113f191a12f859a9e8456b26d. I had nak'd it, and Greg said on the thread that it links that he wasn't going to take it either, especially since it's not his code or his tree, but then, seemingly accidentally, it got pushed up some months later, in what looks like a mistake, with no further discussion in the linked thread. So revert it, since it's clearly not intended. Fixes: ad6bcdad2b67 ("vmgenid: emit uevent when VMGENID updates") Cc: stable@vger.kernel.org Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20230531095119.11202-2-bchalios@amazon.es Signed-off-by: Jason A. Donenfeld --- drivers/virt/vmgenid.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/virt/vmgenid.c b/drivers/virt/vmgenid.c index b67a28da47026..a1c467a0e9f71 100644 --- a/drivers/virt/vmgenid.c +++ b/drivers/virt/vmgenid.c @@ -68,7 +68,6 @@ out: static void vmgenid_notify(struct acpi_device *device, u32 event) { struct vmgenid_state *state = acpi_driver_data(device); - char *envp[] = { "NEW_VMGENID=1", NULL }; u8 old_id[VMGENID_SIZE]; memcpy(old_id, state->this_id, sizeof(old_id)); @@ -76,7 +75,6 @@ static void vmgenid_notify(struct acpi_device *device, u32 event) if (!memcmp(old_id, state->this_id, sizeof(old_id))) return; add_vmfork_randomness(state->this_id, sizeof(state->this_id)); - kobject_uevent_env(&device->dev.kobj, KOBJ_CHANGE, envp); } static const struct acpi_device_id vmgenid_ids[] = { -- cgit 1.2.3-korg