[PATCH] Bluetooth: hci_sync: Protect UUID list traversal

[PATCH] Bluetooth: hci_sync: Protect UUID list traversal

[Chengfeng Ye]

The hci_sync conversion moved class-of-device and EIR generation from an
HCI request built under hdev->lock to asynchronous command sync work.
The worker holds hdev->req_lock, but that lock does not serialize access
to hdev->uuids against add_uuid() and remove_uuid(), which update the
list under hdev->lock.

The following interleaving can therefore occur:

  CPU0 (command sync work)       CPU1 (management socket)
  fetch uuid from the list
                                list_del(&uuid->list)
                                kfree(uuid)
  read uuid->size

KASAN reports the resulting use-after-free:

  BUG: KASAN: slab-use-after-free in eir_create+0xb8f/0xee0
  Read of size 1 at addr ffff88810dbd8620 by task kworker/u17:0/87
  Workqueue: hci0 hci_cmd_sync_work
  Call Trace:
   eir_create+0xb8f/0xee0
   hci_update_eir_sync+0x1c0/0x330
   hci_cmd_sync_work+0x13c/0x290
   process_one_work+0x63a/0x1070
   worker_thread+0x45b/0xd10

  Allocated by task 86:
   __kasan_kmalloc+0x8f/0xa0
   add_uuid+0x18a/0x4b0
   hci_sock_sendmsg+0x1033/0x1ea0

  Freed by task 92:
   __kasan_slab_free+0x43/0x70
   kfree+0x131/0x3c0
   remove_uuid+0x25e/0x560
   hci_sock_sendmsg+0x1033/0x1ea0

Hold hdev->lock while generating and committing the class-of-device and
EIR snapshots.  Release it before sending an HCI command, so controller
waits do not happen under the device lock.  This protects all UUID list
walks in these paths and restores the serialization lost in the command
sync conversion.

Fixes: 161510ccf91c ("Bluetooth: hci_sync: Make use of hci_cmd_sync_queue set 1")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
---
 net/bluetooth/hci_sync.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 532534bc601c..c0b1fc293b49 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -929,12 +929,16 @@ int hci_update_eir_sync(struct hci_dev *hdev)
 
 	memset(&cp, 0, sizeof(cp));
 
+	hci_dev_lock(hdev);
 	eir_create(hdev, cp.data);
 
-	if (memcmp(cp.data, hdev->eir, sizeof(cp.data)) == 0)
+	if (memcmp(cp.data, hdev->eir, sizeof(cp.data)) == 0) {
+		hci_dev_unlock(hdev);
 		return 0;
+	}
 
 	memcpy(hdev->eir, cp.data, sizeof(cp.data));
+	hci_dev_unlock(hdev);
 
 	return __hci_cmd_sync_status(hdev, HCI_OP_WRITE_EIR, sizeof(cp), &cp,
 				     HCI_CMD_TIMEOUT);
@@ -966,6 +970,7 @@ int hci_update_class_sync(struct hci_dev *hdev)
 	if (hci_dev_test_flag(hdev, HCI_SERVICE_CACHE))
 		return 0;
 
+	hci_dev_lock(hdev);
 	cod[0] = hdev->minor_class;
 	cod[1] = hdev->major_class;
 	cod[2] = get_service_classes(hdev);
@@ -973,8 +978,12 @@ int hci_update_class_sync(struct hci_dev *hdev)
 	if (hci_dev_test_flag(hdev, HCI_LIMITED_DISCOVERABLE))
 		cod[1] |= 0x20;
 
-	if (memcmp(cod, hdev->dev_class, 3) == 0)
+	if (memcmp(cod, hdev->dev_class, 3) == 0) {
+		hci_dev_unlock(hdev);
 		return 0;
+	}
+
+	hci_dev_unlock(hdev);
 
 	return __hci_cmd_sync_status(hdev, HCI_OP_WRITE_CLASS_OF_DEV,
 				     sizeof(cod), cod, HCI_CMD_TIMEOUT);
-- 
2.43.0

RE: Bluetooth: hci_sync: Protect UUID list traversal

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2469 bytes --]

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=1130342

---Test result---

Test Summary:
CheckPatch                    PASS      0.74 seconds
VerifyFixes                   PASS      0.13 seconds
VerifySignedoff               PASS      0.13 seconds
GitLint                       PASS      0.33 seconds
SubjectPrefix                 PASS      0.13 seconds
BuildKernel                   PASS      27.55 seconds
CheckAllWarning               PASS      29.81 seconds
CheckSparse                   PASS      31.47 seconds
BuildKernel32                 PASS      26.30 seconds
CheckKernelLLVM               SKIP      0.00 seconds
TestRunnerSetup               PASS      509.68 seconds
TestRunner_l2cap-tester       PASS      60.47 seconds
TestRunner_iso-tester         PASS      80.62 seconds
TestRunner_bnep-tester        PASS      18.94 seconds
TestRunner_mgmt-tester        FAIL      217.73 seconds
TestRunner_rfcomm-tester      PASS      26.46 seconds
TestRunner_sco-tester         PASS      32.41 seconds
TestRunner_ioctl-tester       PASS      27.26 seconds
TestRunner_mesh-tester        FAIL      26.97 seconds
TestRunner_smp-tester         PASS      25.23 seconds
TestRunner_userchan-tester    PASS      20.39 seconds
TestRunner_6lowpan-tester     PASS      22.93 seconds
IncrementalBuild              PASS      25.62 seconds

Details
##############################
Test: CheckKernelLLVM - SKIP
Desc: Build kernel with LLVM + context analysis
Output:
Clang not found
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 494, Passed: 488 (98.8%), Failed: 2, Not Run: 4

Failed Test Cases
Read Exp Feature - Success                           Failed       0.257 seconds
LL Privacy - Unpair 1                                Timed out    1.991 seconds
##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner
Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases
Mesh - Send cancel - 1                               Timed out    2.528 seconds
Mesh - Send cancel - 2                               Timed out    1.988 seconds


https://github.com/bluez/bluetooth-next/pull/457

---
Regards,
Linux Bluetooth

Re: [PATCH] Bluetooth: hci_sync: Protect UUID list traversal

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Mon, 20 Jul 2026 00:24:27 +0800 you wrote:
> The hci_sync conversion moved class-of-device and EIR generation from an
> HCI request built under hdev->lock to asynchronous command sync work.
> The worker holds hdev->req_lock, but that lock does not serialize access
> to hdev->uuids against add_uuid() and remove_uuid(), which update the
> list under hdev->lock.
> 
> The following interleaving can therefore occur:
> 
> [...]

Here is the summary with links:
  - Bluetooth: hci_sync: Protect UUID list traversal
    https://git.kernel.org/bluetooth/bluetooth-next/c/9348bd469f56

You are awesome, thank you!
-- 
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