[PATCH v2] ath9k: backport hw_random API support
Rui Salvaterra
rsalvaterra at gmail.com
Wed Mar 23 06:50:30 PDT 2022
Backport Jason's patch [1] implementing proper hw_random API support for the
ath9k hwrng. The original code invoked add_hwgenerator_randomness to directly
feed ADC entropy into the system pool. Since add_hwgenerator_randomness blocks
until the system is low on entropy, if there is another hw_random API-based
hwrng selected in the system, both of them will race to feed the entropy pool
on wake-up. This unpredictability of the entropy source is a potential security
risk. By turning supported ath9k devices into proper hwrngs, we allow users to
choose one, if any, as they see fit.
[1] https://lore.kernel.org/all/20220216113323.53332-1-Jason@zx2c4.com/
Acked-by: Petr Štetiar <ynezz at true.cz>
Signed-off-by: Rui Salvaterra <rsalvaterra at gmail.com>
---
v2: make it actually build when CONFIG_ATH9K_HWRNG is selected (and rng-core.ko
isn't built-in).
package/kernel/mac80211/ath.mk | 2 +-
...dom-API-instead-of-directly-dumping-.patch | 145 ++++++++++++++++++
2 files changed, 146 insertions(+), 1 deletion(-)
create mode 100644 package/kernel/mac80211/patches/ath9k/020-v5.18-ath9k-use-hw_random-API-instead-of-directly-dumping-.patch
diff --git a/package/kernel/mac80211/ath.mk b/package/kernel/mac80211/ath.mk
index 50b1eed9c8..7c1f4873a8 100644
--- a/package/kernel/mac80211/ath.mk
+++ b/package/kernel/mac80211/ath.mk
@@ -201,7 +201,7 @@ define KernelPackage/ath9k
$(call KernelPackage/mac80211/Default)
TITLE:=Atheros 802.11n PCI wireless cards support
URL:=https://wireless.wiki.kernel.org/en/users/drivers/ath9k
- DEPENDS+= @PCI_SUPPORT||TARGET_ath79 +kmod-ath9k-common
+ DEPENDS+= @PCI_SUPPORT||TARGET_ath79 +ATH9K_HWRNG:kmod-random-core +kmod-ath9k-common
FILES:= \
$(PKG_BUILD_DIR)/drivers/net/wireless/ath/ath9k/ath9k.ko
AUTOLOAD:=$(call AutoProbe,ath9k)
diff --git a/package/kernel/mac80211/patches/ath9k/020-v5.18-ath9k-use-hw_random-API-instead-of-directly-dumping-.patch b/package/kernel/mac80211/patches/ath9k/020-v5.18-ath9k-use-hw_random-API-instead-of-directly-dumping-.patch
new file mode 100644
index 0000000000..e6fcba8a9a
--- /dev/null
+++ b/package/kernel/mac80211/patches/ath9k/020-v5.18-ath9k-use-hw_random-API-instead-of-directly-dumping-.patch
@@ -0,0 +1,145 @@
+From 26a3c8256d1940dbaf0449f0cc4f4c94e321e054 Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason at zx2c4.com>
+Date: Wed, 16 Feb 2022 12:33:23 +0100
+Subject: [PATCH] ath9k: use hw_random API instead of directly dumping into
+ random.c
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Hardware random number generators are supposed to use the hw_random
+framework. This commit turns ath9k's kthread-based design into a proper
+hw_random driver.
+
+Cc: Toke Høiland-Jørgensen <toke at redhat.com>
+Cc: Kalle Valo <kvalo at kernel.org>
+Cc: Rui Salvaterra <rsalvaterra at gmail.com>
+Cc: Dominik Brodowski <linux at dominikbrodowski.net>
+Cc: Herbert Xu <herbert at gondor.apana.org.au>
+Signed-off-by: Jason A. Donenfeld <Jason at zx2c4.com>
+Signed-off-by: Rui Salvaterra <rsalvaterra at gmail.com>
+---
+ drivers/net/wireless/ath/ath9k/ath9k.h | 3 +-
+ drivers/net/wireless/ath/ath9k/rng.c | 72 +++++++++++---------------
+ 2 files changed, 33 insertions(+), 42 deletions(-)
+
+--- a/drivers/net/wireless/ath/ath9k/ath9k.h
++++ b/drivers/net/wireless/ath/ath9k/ath9k.h
+@@ -1071,8 +1071,9 @@ struct ath_softc {
+ #endif
+
+ #ifdef CPTCFG_ATH9K_HWRNG
++ struct hwrng rng_ops;
+ u32 rng_last;
+- struct task_struct *rng_task;
++ char rng_name[sizeof("ath9k_65535")];
+ #endif
+ };
+
+--- a/drivers/net/wireless/ath/ath9k/rng.c
++++ b/drivers/net/wireless/ath/ath9k/rng.c
+@@ -21,11 +21,6 @@
+ #include "hw.h"
+ #include "ar9003_phy.h"
+
+-#define ATH9K_RNG_BUF_SIZE 320
+-#define ATH9K_RNG_ENTROPY(x) (((x) * 8 * 10) >> 5) /* quality: 10/32 */
+-
+-static DECLARE_WAIT_QUEUE_HEAD(rng_queue);
+-
+ static int ath9k_rng_data_read(struct ath_softc *sc, u32 *buf, u32 buf_size)
+ {
+ int i, j;
+@@ -71,61 +66,56 @@ static u32 ath9k_rng_delay_get(u32 fail_
+ return delay;
+ }
+
+-static int ath9k_rng_kthread(void *data)
++static int ath9k_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+ {
+- int bytes_read;
+- struct ath_softc *sc = data;
+- u32 *rng_buf;
+- u32 delay, fail_stats = 0;
+-
+- rng_buf = kmalloc_array(ATH9K_RNG_BUF_SIZE, sizeof(u32), GFP_KERNEL);
+- if (!rng_buf)
+- goto out;
+-
+- while (!kthread_should_stop()) {
+- bytes_read = ath9k_rng_data_read(sc, rng_buf,
+- ATH9K_RNG_BUF_SIZE);
+- if (unlikely(!bytes_read)) {
+- delay = ath9k_rng_delay_get(++fail_stats);
+- wait_event_interruptible_timeout(rng_queue,
+- kthread_should_stop(),
+- msecs_to_jiffies(delay));
+- continue;
++ struct ath_softc *sc = container_of(rng, struct ath_softc, rng_ops);
++ u32 fail_stats = 0, word;
++ int bytes_read = 0;
++
++ for (;;) {
++ if (max & ~3UL)
++ bytes_read = ath9k_rng_data_read(sc, buf, max >> 2);
++ if ((max & 3UL) && ath9k_rng_data_read(sc, &word, 1)) {
++ memcpy(buf + bytes_read, &word, max & 3UL);
++ bytes_read += max & 3UL;
++ memzero_explicit(&word, sizeof(word));
+ }
++ if (!wait || !max || likely(bytes_read) || fail_stats > 110)
++ break;
+
+- fail_stats = 0;
+-
+- /* sleep until entropy bits under write_wakeup_threshold */
+- add_hwgenerator_randomness((void *)rng_buf, bytes_read,
+- ATH9K_RNG_ENTROPY(bytes_read));
++ msleep_interruptible(ath9k_rng_delay_get(++fail_stats));
+ }
+
+- kfree(rng_buf);
+-out:
+- sc->rng_task = NULL;
+-
+- return 0;
++ if (wait && !bytes_read && max)
++ bytes_read = -EIO;
++ return bytes_read;
+ }
+
+ void ath9k_rng_start(struct ath_softc *sc)
+ {
++ static atomic_t serial = ATOMIC_INIT(0);
+ struct ath_hw *ah = sc->sc_ah;
+
+- if (sc->rng_task)
++ if (sc->rng_ops.read)
+ return;
+
+ if (!AR_SREV_9300_20_OR_LATER(ah))
+ return;
+
+- sc->rng_task = kthread_run(ath9k_rng_kthread, sc, "ath9k-hwrng");
+- if (IS_ERR(sc->rng_task))
+- sc->rng_task = NULL;
++ snprintf(sc->rng_name, sizeof(sc->rng_name), "ath9k_%u",
++ (atomic_inc_return(&serial) - 1) & U16_MAX);
++ sc->rng_ops.name = sc->rng_name;
++ sc->rng_ops.read = ath9k_rng_read;
++ sc->rng_ops.quality = 320;
++
++ if (devm_hwrng_register(sc->dev, &sc->rng_ops))
++ sc->rng_ops.read = NULL;
+ }
+
+ void ath9k_rng_stop(struct ath_softc *sc)
+ {
+- if (sc->rng_task) {
+- kthread_stop(sc->rng_task);
+- sc->rng_task = NULL;
++ if (sc->rng_ops.read) {
++ devm_hwrng_unregister(sc->dev, &sc->rng_ops);
++ sc->rng_ops.read = NULL;
+ }
+ }
--
2.35.1
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