kernel-aes67/drivers/char
Jason A. Donenfeld e871abcda3 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:

  [<ffffffd613025ba0>] die+0xa8/0x2fc
  [<ffffffd613027428>] bug_handler+0x44/0xec
  [<ffffffd613016964>] brk_handler+0x90/0x144
  [<ffffffd613041e58>] do_debug_exception+0xa0/0x148
  [<ffffffd61400c208>] el1_dbg+0x60/0x7c
  [<ffffffd61400c000>] el1h_64_sync_handler+0x38/0x90
  [<ffffffd613011294>] el1h_64_sync+0x64/0x6c
  [<ffffffd613102d88>] __might_resched+0x1fc/0x2e8
  [<ffffffd613102b54>] __might_sleep+0x44/0x7c
  [<ffffffd6130b6eac>] cpus_read_lock+0x1c/0xec
  [<ffffffd6132c2820>] static_key_enable+0x14/0x38
  [<ffffffd61400ac08>] crng_set_ready+0x14/0x28
  [<ffffffd6130df4dc>] execute_in_process_context+0xb8/0xf8
  [<ffffffd61400ab30>] _credit_init_bits+0x118/0x1dc
  [<ffffffd6138580c8>] add_timer_randomness+0x264/0x270
  [<ffffffd613857e54>] add_input_randomness+0x38/0x48
  [<ffffffd613a80f94>] input_handle_event+0x2b8/0x490
  [<ffffffd613a81310>] 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 <guoyong.wang@mediatek.com>
Cc: stable@vger.kernel.org
Fixes: f5bda35fba ("random: use static branch for crng_ready()")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2024-04-17 13:53:18 +02:00
..
agp char/agp: remove agp_bridge_data::type 2024-02-16 18:07:13 +01:00
hw_random This update includes the following changes: 2024-03-15 14:46:54 -07:00
ipmi ipmi: Remove usage of the deprecated ida_simple_xx() API 2023-12-19 06:33:45 -06:00
mwave
tpm - Kuan-Wei Chiu has developed the well-named series "lib min_heap: Min 2024-03-14 18:03:09 -07:00
xilinx_hwicap char: xilinx_hwicap: Fix NULL vs IS_ERR() bug 2024-03-07 21:48:38 +00:00
xillybus char: xillybus: Convert to platform remove callback returning void 2024-03-07 21:49:30 +00:00
Kconfig arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
Makefile arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
adi.c
apm-emulation.c
applicom.c applicom: Fix PCI device refcount leak in applicom_init() 2023-01-20 13:05:39 +01:00
applicom.h
bsr.c char: Explicitly include correct DT includes 2023-07-30 18:15:27 +02:00
ds1620.c
dsp56k.c dsp56k: make dsp56k_class a static const structure 2023-06-23 10:27:08 +02:00
dtlk.c
hangcheck-timer.c
hpet.c hpet: remove hpets::hp_clocksource 2024-03-07 21:48:00 +00:00
lp.c char: lp: make lp_class a static const structure 2023-06-23 10:27:11 +02:00
mem.c Char/Misc and other driver changes for 6.7-rc1 2023-11-03 14:51:08 -10:00
misc.c char: misc: make misc_class a static const structure 2023-06-23 10:27:15 +02:00
nsc_gpio.c
nvram.c
nwbutton.c
nwbutton.h
nwflash.c
pc8736x_gpio.c
powernv-op-panel.c
ppdev.c ppdev: Remove usage of the deprecated ida_simple_xx() API 2024-01-04 16:43:20 +01:00
ps3flash.c
random.c random: handle creditable entropy from atomic process context 2024-04-17 13:53:18 +02:00
scx200_gpio.c
sonypi.c char: convert to new timestamp accessors 2023-10-18 13:26:16 +02:00
tlclk.c
toshiba.c
ttyprintk.c tty: ttyprintk: convert to u8 and size_t 2023-12-08 12:02:38 +01:00
uv_mmtimer.c
virtio_console.c tty: hvc: convert to u8 and size_t 2023-12-08 12:02:37 +01:00