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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, "Ivan T. Ivanov" <iivanov@suse.de>,
	Dominik Brodowski <linux@dominikbrodowski.net>,
	"Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: [PATCH 5.15 36/41] random: fix crash on multiple early calls to add_bootloader_randomness()
Date: Fri, 14 Jan 2022 09:16:36 +0100	[thread overview]
Message-ID: <20220114081546.372351334@linuxfoundation.org> (raw)
In-Reply-To: <20220114081545.158363487@linuxfoundation.org>

From: Dominik Brodowski <linux@dominikbrodowski.net>

commit f7e67b8e803185d0aabe7f29d25a35c8be724a78 upstream.

Currently, if CONFIG_RANDOM_TRUST_BOOTLOADER is enabled, multiple calls
to add_bootloader_randomness() are broken and can cause a NULL pointer
dereference, as noted by Ivan T. Ivanov. This is not only a hypothetical
problem, as qemu on arm64 may provide bootloader entropy via EFI and via
devicetree.

On the first call to add_hwgenerator_randomness(), crng_fast_load() is
executed, and if the seed is long enough, crng_init will be set to 1.
On subsequent calls to add_bootloader_randomness() and then to
add_hwgenerator_randomness(), crng_fast_load() will be skipped. Instead,
wait_event_interruptible() and then credit_entropy_bits() will be called.
If the entropy count for that second seed is large enough, that proceeds
to crng_reseed().

However, both wait_event_interruptible() and crng_reseed() depends
(at least in numa_crng_init()) on workqueues. Therefore, test whether
system_wq is already initialized, which is a sufficient indicator that
workqueue_init_early() has progressed far enough.

If we wind up hitting the !system_wq case, we later want to do what
would have been done there when wqs are up, so set a flag, and do that
work later from the rand_initialize() call.

Reported-by: Ivan T. Ivanov <iivanov@suse.de>
Fixes: 18b915ac6b0a ("efi/random: Treat EFI_RNG_PROTOCOL output as bootloader randomness")
Cc: stable@vger.kernel.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
[Jason: added crng_need_done state and related logic.]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/char/random.c |   56 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 36 insertions(+), 20 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -461,6 +461,7 @@ static struct crng_state primary_crng =
  * its value (from 0->1->2).
  */
 static int crng_init = 0;
+static bool crng_need_final_init = false;
 #define crng_ready() (likely(crng_init > 1))
 static int crng_init_cnt = 0;
 static unsigned long crng_global_init_time = 0;
@@ -828,6 +829,36 @@ static void __init crng_initialize_prima
 	crng->init_time = jiffies - CRNG_RESEED_INTERVAL - 1;
 }
 
+static void crng_finalize_init(struct crng_state *crng)
+{
+	if (crng != &primary_crng || crng_init >= 2)
+		return;
+	if (!system_wq) {
+		/* We can't call numa_crng_init until we have workqueues,
+		 * so mark this for processing later. */
+		crng_need_final_init = true;
+		return;
+	}
+
+	invalidate_batched_entropy();
+	numa_crng_init();
+	crng_init = 2;
+	process_random_ready_list();
+	wake_up_interruptible(&crng_init_wait);
+	kill_fasync(&fasync, SIGIO, POLL_IN);
+	pr_notice("crng init done\n");
+	if (unseeded_warning.missed) {
+		pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
+			  unseeded_warning.missed);
+		unseeded_warning.missed = 0;
+	}
+	if (urandom_warning.missed) {
+		pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
+			  urandom_warning.missed);
+		urandom_warning.missed = 0;
+	}
+}
+
 #ifdef CONFIG_NUMA
 static void do_numa_crng_init(struct work_struct *work)
 {
@@ -982,25 +1013,7 @@ static void crng_reseed(struct crng_stat
 	memzero_explicit(&buf, sizeof(buf));
 	WRITE_ONCE(crng->init_time, jiffies);
 	spin_unlock_irqrestore(&crng->lock, flags);
-	if (crng == &primary_crng && crng_init < 2) {
-		invalidate_batched_entropy();
-		numa_crng_init();
-		crng_init = 2;
-		process_random_ready_list();
-		wake_up_interruptible(&crng_init_wait);
-		kill_fasync(&fasync, SIGIO, POLL_IN);
-		pr_notice("crng init done\n");
-		if (unseeded_warning.missed) {
-			pr_notice("%d get_random_xx warning(s) missed due to ratelimiting\n",
-				  unseeded_warning.missed);
-			unseeded_warning.missed = 0;
-		}
-		if (urandom_warning.missed) {
-			pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
-				  urandom_warning.missed);
-			urandom_warning.missed = 0;
-		}
-	}
+	crng_finalize_init(crng);
 }
 
 static void _extract_crng(struct crng_state *crng,
@@ -1780,6 +1793,8 @@ static void __init init_std_data(struct
 int __init rand_initialize(void)
 {
 	init_std_data(&input_pool);
+	if (crng_need_final_init)
+		crng_finalize_init(&primary_crng);
 	crng_initialize_primary(&primary_crng);
 	crng_global_init_time = jiffies;
 	if (ratelimit_disable) {
@@ -2288,7 +2303,8 @@ void add_hwgenerator_randomness(const ch
 	 * We'll be woken up again once below random_write_wakeup_thresh,
 	 * or when the calling thread is about to terminate.
 	 */
-	wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+	wait_event_interruptible(random_write_wait,
+			!system_wq || kthread_should_stop() ||
 			ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
 	mix_pool_bytes(poolp, buffer, count);
 	credit_entropy_bits(poolp, entropy);



  parent reply	other threads:[~2022-01-14  8:22 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-14  8:16 [PATCH 5.15 00/41] 5.15.15-rc1 review Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 01/41] s390/kexec: handle R_390_PLT32DBL rela in arch_kexec_apply_relocations_add() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 02/41] workqueue: Fix unbind_workers() VS wq_worker_running() race Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 03/41] staging: r8188eu: switch the led off during deinit Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 04/41] bpf: Fix out of bounds access from invalid *_or_null type verification Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 05/41] Bluetooth: btusb: Add protocol for MediaTek bluetooth devices(MT7922) Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 06/41] Bluetooth: btusb: Add the new support ID for Realtek RTL8852A Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 07/41] Bluetooth: btusb: Add support for IMC Networks Mediatek Chip(MT7921) Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 08/41] Bbluetooth: btusb: Add another Bluetooth part for Realtek 8852AE Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 09/41] Bluetooth: btusb: fix memory leak in btusb_mtk_submit_wmt_recv_urb() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 10/41] Bluetooth: btusb: enable Mediatek to support AOSP extension Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 11/41] Bluetooth: btusb: Add one more Bluetooth part for the Realtek RTL8852AE Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 12/41] Bluetooth: btusb: Add the new support IDs for WCN6855 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 13/41] fget: clarify and improve __fget_files() implementation Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 14/41] Bluetooth: btusb: Add one more Bluetooth part for WCN6855 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 15/41] Bluetooth: btusb: Add two more Bluetooth parts " Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 16/41] Bluetooth: btusb: Add support for Foxconn MT7922A Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 17/41] Bluetooth: btintel: Fix broken LED quirk for legacy ROM devices Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 18/41] Bluetooth: btusb: Add support for Foxconn QCA 0xe0d0 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 19/41] Bluetooth: bfusb: fix division by zero in send path Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 20/41] ARM: dts: exynos: Fix BCM4330 Bluetooth reset polarity in I9100 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 21/41] USB: core: Fix bug in resuming hubs handling of wakeup requests Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 22/41] USB: Fix "slab-out-of-bounds Write" bug in usb_hcd_poll_rh_status Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 23/41] ath11k: Fix buffer overflow when scanning with extraie Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 24/41] mmc: sdhci-pci: Add PCI ID for Intel ADL Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 25/41] Bluetooth: add quirk disabling LE Read Transmit Power Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 26/41] Bluetooth: btbcm: disable read tx power for some Macs with the T2 Security chip Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 27/41] Bluetooth: btbcm: disable read tx power for MacBook Air 8,1 and 8,2 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 28/41] veth: Do not record rx queue hint in veth_xmit Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 29/41] mfd: intel-lpss: Fix too early PM enablement in the ACPI ->probe() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 30/41] x86/mce: Remove noinstr annotation from mce_setup() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 31/41] can: gs_usb: fix use of uninitialized variable, detach device on reception of invalid USB data Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 32/41] can: isotp: convert struct tpcon::{idx,len} to unsigned int Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 33/41] can: gs_usb: gs_can_start_xmit(): zero-initialize hf->{flags,reserved} Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 34/41] random: fix data race on crng_node_pool Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 35/41] random: fix data race on crng init time Greg Kroah-Hartman
2022-01-14  8:16 ` Greg Kroah-Hartman [this message]
2022-01-14  8:16 ` [PATCH 5.15 37/41] platform/x86/intel: hid: add quirk to support Surface Go 3 Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 38/41] media: Revert "media: uvcvideo: Set unique vdev name based in type" Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 39/41] staging: wlan-ng: Avoid bitwise vs logical OR warning in hfa384x_usb_throttlefn() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 40/41] drm/i915: Avoid bitwise vs logical OR warning in snb_wm_latency_quirk() Greg Kroah-Hartman
2022-01-14  8:16 ` [PATCH 5.15 41/41] staging: greybus: fix stack size warning with UBSAN Greg Kroah-Hartman
2022-01-14 17:43 ` [PATCH 5.15 00/41] 5.15.15-rc1 review Naresh Kamboju
2022-01-14 18:09 ` Jon Hunter
2022-01-14 19:59 ` Ron Economos
2022-01-15  8:14   ` Greg Kroah-Hartman
2022-01-15 11:52     ` Ron Economos
2022-01-15 12:15       ` Greg Kroah-Hartman
2022-01-15 12:31         ` Ron Economos
2022-01-14 22:29 ` Florian Fainelli
2022-01-14 23:32 ` Fox Chen
2022-01-15  0:24 ` Shuah Khan
2022-01-15 11:03 ` Sudip Mukherjee
2022-01-15 14:47 ` Andrei Rabusov
2022-01-15 16:39 ` Guenter Roeck
2022-01-15 16:48 ` Jeffrin Jose T

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