On Tue, May 21, 2024 at 03:37:16PM -0400, Nícolas F. R. A. Prado wrote: > > FWIW this patch fixes the warning. So feel free to add > > Tested-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx> Could you please test this patch instead? ---8<--- A potential deadlock was reported with the config file at https://web.archive.org/web/20240522052129/https://0x0.st/XPN_.txt In this particular configuration, the deadlock doesn't exist because the warning triggered at a point before modules were even available. However, the deadlock can be real because any module loaded would invoke async_synchronize_full. The issue is spurious for software crypto algorithms which aren't themselves involved in async probing. However, it would be hard to avoid for a PCI crypto driver using async probing. In this particular call trace, the problem is easily avoided because the only reason the module is being requested during probing is the add_early_randomness call in the hwrng core. This feature is vestigial since there is now a kernel thread dedicated to doing exactly this. So remove add_early_randomness as it is no longer needed. Reported-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx> Reported-by: Eric Biggers <ebiggers@xxxxxxxxxx> Fixes: 1b6d7f9eb150 ("tpm: add session encryption protection to tpm2_get_random()") Link: https://lore.kernel.org/r/119dc5ed-f159-41be-9dda-1a056f29888d@notapiano/ Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index f5c71a617a99..4084df65c9fa 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -64,19 +64,6 @@ static size_t rng_buffer_size(void) return RNG_BUFFER_SIZE; } -static void add_early_randomness(struct hwrng *rng) -{ - int bytes_read; - - mutex_lock(&reading_mutex); - bytes_read = rng_get_data(rng, rng_fillbuf, 32, 0); - mutex_unlock(&reading_mutex); - if (bytes_read > 0) { - size_t entropy = bytes_read * 8 * rng->quality / 1024; - add_hwgenerator_randomness(rng_fillbuf, bytes_read, entropy, false); - } -} - static inline void cleanup_rng(struct kref *kref) { struct hwrng *rng = container_of(kref, struct hwrng, ref); @@ -340,13 +327,12 @@ static ssize_t rng_current_store(struct device *dev, const char *buf, size_t len) { int err; - struct hwrng *rng, *old_rng, *new_rng; + struct hwrng *rng, *new_rng; err = mutex_lock_interruptible(&rng_mutex); if (err) return -ERESTARTSYS; - old_rng = current_rng; if (sysfs_streq(buf, "")) { err = enable_best_rng(); } else { @@ -362,11 +348,8 @@ static ssize_t rng_current_store(struct device *dev, new_rng = get_current_rng_nolock(); mutex_unlock(&rng_mutex); - if (new_rng) { - if (new_rng != old_rng) - add_early_randomness(new_rng); + if (new_rng) put_rng(new_rng); - } return err ? : len; } @@ -544,7 +527,6 @@ int hwrng_register(struct hwrng *rng) { int err = -EINVAL; struct hwrng *tmp; - bool is_new_current = false; if (!rng->name || (!rng->data_read && !rng->read)) goto out; @@ -573,25 +555,8 @@ int hwrng_register(struct hwrng *rng) err = set_current_rng(rng); if (err) goto out_unlock; - /* to use current_rng in add_early_randomness() we need - * to take a ref - */ - is_new_current = true; - kref_get(&rng->ref); } mutex_unlock(&rng_mutex); - if (is_new_current || !rng->init) { - /* - * Use a new device's input to add some randomness to - * the system. If this rng device isn't going to be - * used right away, its init function hasn't been - * called yet by set_current_rng(); so only use the - * randomness from devices that don't need an init callback - */ - add_early_randomness(rng); - } - if (is_new_current) - put_rng(rng); return 0; out_unlock: mutex_unlock(&rng_mutex); @@ -602,12 +567,11 @@ EXPORT_SYMBOL_GPL(hwrng_register); void hwrng_unregister(struct hwrng *rng) { - struct hwrng *old_rng, *new_rng; + struct hwrng *new_rng; int err; mutex_lock(&rng_mutex); - old_rng = current_rng; list_del(&rng->list); complete_all(&rng->dying); if (current_rng == rng) { @@ -626,11 +590,8 @@ void hwrng_unregister(struct hwrng *rng) } else mutex_unlock(&rng_mutex); - if (new_rng) { - if (old_rng != new_rng) - add_early_randomness(new_rng); + if (new_rng) put_rng(new_rng); - } wait_for_completion(&rng->cleanup_done); } -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
