[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]

[-- Attachment #1: Type: text/plain, Size: 1468 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=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

[PATCH v2] Bluetooth: virtio_bt: avoid OOB read of build info string

[HyeongJun An]

The virtbt_setup_zephyr() sends the Zephyr vendor command 0xfc08 (Read
Build Information) and hands the response to bt_dev_info() and
hci_set_fw_info() as a "%s" string starting at skb->data + 1, without
checking the length. A backend that answers with status only leaves that
pointer past the end of the received data, so the walk reads adjacent
slab memory until it meets a NUL. Those bytes reach the kernel log and
the firmware-info debugfs file.

To fix this, print the string with a bounded "%.*s" limited to
skb->len - 1. A short or unterminated response then prints as much as
arrived instead of failing setup.

This mirrors commit dd068ef04412 ("Bluetooth: bpa10x: avoid OOB read of
revision string in bpa10x_setup()"), which fixed the identical pattern.

Fixes: afd2daa26c7a ("Bluetooth: Add support for virtio transport driver")
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
Assisted-by: Claude:claude-opus-4-8
---
v2: shortened the subject to fit the list's 80-character limit
    tightened the message

v1: https://lore.kernel.org/linux-bluetooth/20260715121628.1590321-1-sammiee5311@gmail.com/

 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: [v2] Bluetooth: virtio_bt: avoid OOB read of build info string

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 1181 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=1137030

---Test result---

Test Summary:
CheckPatch                    PASS      0.57 seconds
VerifyFixes                   PASS      0.07 seconds
VerifySignedoff               PASS      0.07 seconds
GitLint                       PASS      0.21 seconds
SubjectPrefix                 PASS      0.06 seconds
BuildKernel                   PASS      27.24 seconds
CheckAllWarning               PASS      30.16 seconds
CheckSparse                   PASS      28.12 seconds
BuildKernel32                 PASS      26.44 seconds
CheckKernelLLVM               SKIP      0.00 seconds
TestRunnerSetup               PASS      501.00 seconds
IncrementalBuild              PASS      25.65 seconds

Details
##############################
Test: CheckKernelLLVM - SKIP
Desc: Build kernel with LLVM + context analysis
Output:
Clang not found


https://github.com/bluez/bluetooth-next/pull/512

---
Regards,
Linux Bluetooth

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

[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 Wed, 15 Jul 2026 21:16:28 +0900 you wrote:
> 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);
> 
> [...]

Here is the summary with links:
  - Bluetooth: virtio_bt: avoid OOB read of build info string in virtbt_setup_zephyr()
    https://git.kernel.org/bluetooth/bluetooth-next/c/d264c90ca22e

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH v2] Bluetooth: virtio_bt: avoid OOB read of build info string

[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 Thu, 30 Jul 2026 10:57:28 +0900 you wrote:
> The virtbt_setup_zephyr() sends the Zephyr vendor command 0xfc08 (Read
> Build Information) and hands the response to bt_dev_info() and
> hci_set_fw_info() as a "%s" string starting at skb->data + 1, without
> checking the length. A backend that answers with status only leaves that
> pointer past the end of the received data, so the walk reads adjacent
> slab memory until it meets a NUL. Those bytes reach the kernel log and
> the firmware-info debugfs file.
> 
> [...]

Here is the summary with links:
  - [v2] Bluetooth: virtio_bt: avoid OOB read of build info string
    https://git.kernel.org/bluetooth/bluetooth-next/c/d264c90ca22e

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html