From: Jason A. Donenfeld Jason@zx2c4.com
commit 36cb6494429bd64b27b7ff8b4af56f8e526da2b4 upstream.
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_EJUGQtd8JiCkiEHytGgDsFGTEjs0c00... Link: https://lore.kernel.org/lkml/CAO+Okf5k+C+SE6pMVfPf-d8MfVPVq4PO7EY8Hys_DVXten... 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 Acked-by: Kalle Valo kvalo@kernel.org Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/hw_random/core.c | 19 +++++++++++++++---- drivers/net/wireless/ath/ath9k/rng.c | 3 ++- include/linux/hw_random.h | 3 +++ 3 files changed, 20 insertions(+), 5 deletions(-)
--- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -507,16 +507,17 @@ 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 +571,7 @@ 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 +619,7 @@ 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 +688,14 @@ void devm_hwrng_unregister(struct device } 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; --- 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 * 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) --- 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 de 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_ */