[PATCH] Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()

[PATCH] Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()

[HyeongJun An]

virtbt_setup_zephyr() sends the Zephyr vendor command 0xfc08 (Read Build
Information) and passes the response to bt_dev_info() and hci_set_fw_info()
as a "%s" string starting at skb->data + 1, without checking the length:

  bt_dev_info(hdev, "%s", (char *)(skb->data + 1));
  hci_set_fw_info(hdev, "%s", skb->data + 1);

A backend that returns a one-byte response (status only) leaves
skb->data + 1 past the end of the received data, and the %s walk reads
adjacent slab memory until it meets a NUL. The same happens when the
payload is not NUL-terminated within skb->len. The out-of-bounds bytes
end up in the kernel log and the firmware-info debugfs file.

Print the build-information string with a bounded "%.*s" limited to
skb->len - 1 instead. This keeps the string readable for well-behaved
backends while never reading past the received data, and does not fail
setup, so a backend returning a short or unterminated response keeps
working.

This mirrors commit dd068ef04412 ("Bluetooth: bpa10x: avoid OOB read of
revision string in bpa10x_setup()"), which fixed the identical pattern;
the virtio backend is likewise treated as untrusted for the receive path.

Fixes: afd2daa26c7a ("Bluetooth: Add support for virtio transport driver")
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Assisted-by: Claude:claude-opus-4-8
---
 drivers/bluetooth/virtio_bt.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c
index 140ab55c9fc5..c20d54088c8c 100644
--- a/drivers/bluetooth/virtio_bt.c
+++ b/drivers/bluetooth/virtio_bt.c
@@ -120,9 +120,13 @@ static int virtbt_setup_zephyr(struct hci_dev *hdev)
 	if (IS_ERR(skb))
 		return PTR_ERR(skb);
 
-	bt_dev_info(hdev, "%s", (char *)(skb->data + 1));
+	/* Bounded print: the backend controls skb->len. */
+	if (skb->len > 1) {
+		int len = skb->len - 1;
 
-	hci_set_fw_info(hdev, "%s", skb->data + 1);
+		bt_dev_info(hdev, "%.*s", len, (char *)(skb->data + 1));
+		hci_set_fw_info(hdev, "%.*s", len, skb->data + 1);
+	}
 
 	kfree_skb(skb);
 	return 0;
-- 
2.43.0

RE: Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()

[bluez.test.bot]

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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=1128120

---Test result---

Test Summary:
CheckPatch                    PASS      0.53 seconds
VerifyFixes                   PASS      0.09 seconds
VerifySignedoff               PASS      0.09 seconds
GitLint                       FAIL      0.23 seconds
SubjectPrefix                 PASS      0.08 seconds
BuildKernel                   PASS      20.76 seconds
CheckAllWarning               PASS      23.23 seconds
CheckSparse                   PASS      22.23 seconds
BuildKernel32                 PASS      21.30 seconds
CheckKernelLLVM               SKIP      0.00 seconds
TestRunnerSetup               PASS      381.35 seconds
IncrementalBuild              PASS      19.67 seconds

Details
##############################
Test: GitLint - FAIL
Desc: Run gitlint
Output:
Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()

1: T1 Title exceeds max length (82>80): "Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()"
##############################
Test: CheckKernelLLVM - SKIP
Desc: Build kernel with LLVM + context analysis
Output:
Clang not found


https://github.com/bluez/bluetooth-next/pull/444

---
Regards,
Linux Bluetooth