FAILED: patch "[PATCH] Bluetooth: hci_sync: Fix command skb lifetime during scan" failed to apply to 6.6-stable tree

PATCH New [email protected] 2 participants 2 messages Oct 12 – Oct 13

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Stable branch Bluetooth

lore

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lore

[email protected]

author maintainer

2026-10-12 15:26 UTC #0 lore raw

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 9af12272061d206af8bc3e40215cb694421ab73a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026101207-gamma-undermost-7763@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9af12272061d206af8bc3e40215cb694421ab73a Mon Sep 17 00:00:00 2001
From: Chengfeng Ye <[email protected]>
Date: Mon, 5 Oct 2026 00:26:12 +0800
Subject: [PATCH] Bluetooth: hci_sync: Fix command skb lifetime during scan
setup

During PA sync scan setup, hci_le_set_ext_scan_param_sync() gets the address used for the PA_LINK lookup from hci_sent_cmd_data(). The returned pointer borrows storage from sent_cmd or req_skb, without holding a reference to either skb.

The scan worker runs on req_workqueue while hci_cmd_work() runs on the separate device workqueue. After the scan worker loads sent_cmd, the command worker can free and replace it before hci_sent_cmd_data() dereferences the skb. The command payload can also be freed between returning from the helper and comparing the address. The connection lookup's RCU critical section does not protect the command skb.

KASAN reported:

  BUG: KASAN: slab-use-after-free in hci_sent_cmd_data+0x27c/0x2f0
  Workqueue: hci0 hci_cmd_sync_work
  Call Trace:
   hci_sent_cmd_data+0x27c/0x2f0
   hci_le_set_scan_param_sync+0x43a/0x850
   hci_passive_scan_sync+0xb09/0x1460
   hci_update_passive_scan_sync+0x47c/0x6e0
   hci_le_pa_create_sync+0x200/0xa70
   hci_cmd_sync_work+0x13c/0x290

  Allocated by task 95:
   skb_clone+0x13f/0x340
   hci_cmd_work+0x2a9/0x7e0

  Freed by task 95:
   kmem_cache_free+0xba/0x3a0
   hci_cmd_work+0x29c/0x7e0

Use hdev->lock to serialize the address snapshot with sent_cmd replacement. Protect req_skb replacement and completion cleanup with the same lock because the helper falls back to that skb. Copy the address before releasing the lock and use the copy for the existing RCU-protected connection lookup. Release the mutex before sending or waiting for commands, preserving the lookup and completion ordering.

Fixes 22cbf4f84c00 ("Bluetooth: hci_sync: Use QoS to determine which PHY to scan")

Cc [email protected]

Assisted-by GPT-6 Astra

Signed-off-by Chengfeng Ye <[email protected]>

Signed-off-by Luiz Augusto von Dentz <[email protected]>

net/bluetooth/hci_core.c +4 -0

index 2076689eb302..74d9865e08c2 100644
@@ -4115,9 +4115,11 @@ static int hci_send_cmd_sync(struct hci_dev *hdev, struct sk_buff *skb)
 
 	bt_dev_dbg(hdev, "skb %p", skb);
 
+	hci_dev_lock(hdev);
 	kfree_skb(hdev->sent_cmd);
 
 	hdev->sent_cmd = skb_clone(skb, GFP_KERNEL);
+	hci_dev_unlock(hdev);
 	if (!hdev->sent_cmd) {
 		skb_queue_head(&hdev->cmd_q, skb);
 		queue_work(hdev->workqueue, &hdev->cmd_work);

@@ -4138,8 +4140,10 @@ static int hci_send_cmd_sync(struct hci_dev *hdev, struct sk_buff *skb)
 
 	if (READ_ONCE(hdev->req_status) == HCI_REQ_PEND &&
 	    !hci_dev_test_and_set_flag(hdev, HCI_CMD_PENDING)) {
+		hci_dev_lock(hdev);
 		kfree_skb(hdev->req_skb);
 		hdev->req_skb = skb_get(hdev->sent_cmd);
+		hci_dev_unlock(hdev);
 	}
 
 	return err;

net/bluetooth/hci_sync.c +9 -1

index c01c8b58d9e8..a92a81846e9d 100644
@@ -32,8 +32,10 @@ static void hci_cmd_sync_complete(struct hci_dev *hdev, u8 result, u16 opcode,
 	WRITE_ONCE(hdev->req_status, HCI_REQ_DONE);
 
 	/* Free the request command so it is not used as response */
+	hci_dev_lock(hdev);
 	kfree_skb(hdev->req_skb);
 	hdev->req_skb = NULL;
+	hci_dev_unlock(hdev);
 
 	if (skb) {
 		struct sock *sk = hci_skb_sk(skb);

@@ -3064,15 +3066,21 @@ static int hci_le_set_ext_scan_param_sync(struct hci_dev *hdev, u8 type,
 	 */
 	if (hci_dev_test_flag(hdev, HCI_PA_SYNC)) {
 		struct hci_cp_le_add_to_accept_list *sent;
+		bdaddr_t bdaddr;
 
+		hci_dev_lock(hdev);
 		sent = hci_sent_cmd_data(hdev, HCI_OP_LE_ADD_TO_ACCEPT_LIST);
+		if (sent)
+			bacpy(&bdaddr, &sent->bdaddr);
+		hci_dev_unlock(hdev);
+
 		if (sent) {
 			struct hci_conn *conn;
 
 			rcu_read_lock();
 
 			conn = hci_conn_hash_lookup_ba(hdev, PA_LINK,
-						       &sent->bdaddr);
+						       &bdaddr);
 			if (conn) {
 				struct bt_iso_qos *qos = &conn->iso_qos;

Sasha Levin

maintainer

2026-10-13 16:20 UTC #1 lore raw

PATCH 1/1 Bluetooth: hci_sync: Fix command skb lifetime during scan setup

From: Chengfeng Ye <[email protected]>

[ Upstream commit 9af12272061d206af8bc3e40215cb694421ab73a ]