| Message ID | YuJjXI+tuiCcixbd@gondor.apana.org.au |
|---|---|
| State | New |
| Headers | show |
| Series | [v12] hwrng: core - let sleep be interrupted when unregistering hwrng | expand |
On 28 July 2022 12:22:20 CEST, Herbert Xu <herbert@gondor.apana.org.au> wrote: >From: Jason A. Donenfeld <Jason@zx2c4.com> > >There are two deadlock scenarios that need addressing, which cause >problems when the computer goes to sleep, the interface is set down, and >hwrng_unregister() is called. When the deadlock is hit, sleep is delayed >for tens of seconds, causing it to fail. These scenarios are: > >1) The hwrng kthread can't be stopped while it's sleeping, because it > uses msleep_interruptible() which does not react to kthread_stop. > >2) A normal user thread can't be interrupted by hwrng_unregister() while > it's sleeping, because hwrng_unregister() is called from elsewhere. > >We solve both issues by add a completion object called dying that >fulfils waiters once we have started the process in hwrng_unregister. > >At the same time, we should cleanup a common and useless dmesg splat >in the same area. > >Cc: <stable@vger.kernel.org> >Reported-by: Gregory Erwin <gregerwin256@gmail.com> >Fixes: fcd09c90c3c5 ("ath9k: use hw_random API instead of directly dumping into random.c") >Link: https://lore.kernel.org/all/CAO+Okf6ZJC5-nTE_EJUGQtd8JiCkiEHytGgDsFGTEjs0c00giw@mail.gmail.com/ >Link: https://lore.kernel.org/lkml/CAO+Okf5k+C+SE6pMVfPf-d8MfVPVq4PO7EY8Hys_DVXtent3HA@mail.gmail.com/ >Link: https://bugs.archlinux.org/task/75138 >Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> >Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 16f227b995e8..21dce7acf086 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -507,16 +508,17 @@ static int hwrng_fillfn(void *unused) rng->quality = current_quality; /* obsolete */ quality = rng->quality; mutex_unlock(&reading_mutex); + + if (rc <= 0) + hwrng_msleep(rng, 10000); + put_rng(rng); if (!quality) break; - if (rc <= 0) { - pr_warn("hwrng: no data available\n"); - msleep_interruptible(10000); + if (rc <= 0) continue; - } /* If we cannot credit at least one bit of entropy, * keep track of the remainder for the next iteration @@ -570,6 +572,7 @@ int hwrng_register(struct hwrng *rng) init_completion(&rng->cleanup_done); complete(&rng->cleanup_done); + init_completion(&rng->dying); if (!current_rng || (!cur_rng_set_by_user && rng->quality > current_rng->quality)) { @@ -617,6 +620,7 @@ void hwrng_unregister(struct hwrng *rng) old_rng = current_rng; list_del(&rng->list); + complete_all(&rng->dying); if (current_rng == rng) { err = enable_best_rng(); if (err) { @@ -685,6 +689,14 @@ void devm_hwrng_unregister(struct device *dev, struct hwrng *rng) } EXPORT_SYMBOL_GPL(devm_hwrng_unregister); +long hwrng_msleep(struct hwrng *rng, unsigned int msecs) +{ + unsigned long timeout = msecs_to_jiffies(msecs) + 1; + + return wait_for_completion_interruptible_timeout(&rng->dying, timeout); +} +EXPORT_SYMBOL_GPL(hwrng_msleep); + static int __init hwrng_modinit(void) { int ret; diff --git a/drivers/net/wireless/ath/ath9k/rng.c b/drivers/net/wireless/ath/ath9k/rng.c index cb5414265a9b..58c0ab01771b 100644 --- a/drivers/net/wireless/ath/ath9k/rng.c +++ b/drivers/net/wireless/ath/ath9k/rng.c @@ -83,7 +83,8 @@ static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait) if (!wait || !max || likely(bytes_read) || fail_stats > 110) break; - msleep_interruptible(ath9k_rng_delay_get(++fail_stats)); + if (hwrng_msleep(rng, ath9k_rng_delay_get(++fail_stats))) + break; } if (wait && !bytes_read && max) diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h index aa1d4da03538..77c2885c4c13 100644 --- a/include/linux/hw_random.h +++ b/include/linux/hw_random.h @@ -50,6 +50,7 @@ struct hwrng { struct list_head list; struct kref ref; struct completion cleanup_done; + struct completion dying; }; struct device; @@ -61,4 +62,6 @@ extern int devm_hwrng_register(struct device *dev, struct hwrng *rng); extern void hwrng_unregister(struct hwrng *rng); extern void devm_hwrng_unregister(struct device *dve, struct hwrng *rng); +extern long hwrng_msleep(struct hwrng *rng, unsigned int msecs); + #endif /* LINUX_HWRANDOM_H_ */