If we have a register/unregister too fast, it can happen that the kthread is not yet started when kthread_stop is called, and this seems to leave a corrupted or uninitialized kthread struct. This is detected by the WARN_ON at kernel/kthread.c:75 and later causes a page domain fault. Wait for the kthread to start the same way as drivers/base/devtmpfs.c does wait for kdevtmpfs thread to start using setup_done completion. Signed-off-by: Marek Vasut <marex@xxxxxxx> --- This is a follow-up on second part of V2 of work by Luca Dariz: https://lore.kernel.org/all/AM6PR06MB5400DAFE0551F1D468B728FBAB889@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ --- Cc: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> Cc: Harald Freudenberger <freude@xxxxxxxxxxxxx> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Cc: Li Zhijian <lizhijian@xxxxxxxxxxx> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> Cc: Olivia Mackall <olivia@xxxxxxxxxxx> Cc: linux-crypto@xxxxxxxxxxxxxxx --- drivers/char/hw_random/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 5be26f4e9d975..bb1f4ba602b1d 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -55,6 +55,7 @@ MODULE_PARM_DESC(default_quality, static void drop_current_rng(void); static int hwrng_init(struct hwrng *rng); static int hwrng_fillfn(void *unused); +static DECLARE_COMPLETION(setup_done); static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size, int wait); @@ -472,6 +473,7 @@ static int hwrng_fillfn(void *unused) size_t entropy, entropy_credit = 0; /* in 1/1024 of a bit */ long rc; + complete(&setup_done); while (!kthread_should_stop()) { unsigned short quality; struct hwrng *rng; @@ -669,13 +671,15 @@ static int __init hwrng_modinit(void) if (ret) goto err_miscdev; - hwrng_fill = kthread_create(hwrng_fillfn, NULL, "hwrng"); + hwrng_fill = kthread_run(hwrng_fillfn, NULL, "hwrng"); if (IS_ERR(hwrng_fill)) { ret = PTR_ERR(hwrng_fill); pr_err("hwrng_fill thread creation failed (%d)\n", ret); goto err_kthread; } + wait_for_completion(&setup_done); + ret = kthread_park(hwrng_fill); if (ret) goto err_park; -- 2.45.2
