[PATCH v3] Bluetooth: Fix double free in hci_conn_cleanup

[PATCH v3] Bluetooth: Fix double free in hci_conn_cleanup

[Bastien Nocera]

From: ZhengHan Wang <wzhmmmmm@gmail.com>

syzbot reports a slab use-after-free in hci_conn_hash_flush [1].
After releasing an object using hci_conn_del_sysfs in the
hci_conn_cleanup function, releasing the same object again
using the hci_dev_put and hci_conn_put functions causes a double free.
Here's a simplified flow:

hci_conn_del_sysfs:
  hci_dev_put
    put_device
      kobject_put
        kref_put
          kobject_release
            kobject_cleanup
              kfree_const
                kfree(name)

hci_dev_put:
  ...
    kfree(name)

hci_conn_put:
  put_device
    ...
      kfree(name)

This patch drop the hci_dev_put and hci_conn_put function
call in hci_conn_cleanup function, because the object is
freed in hci_conn_del_sysfs function.

This patch also fixes the refcounting in hci_conn_add_sysfs() and
hci_conn_del_sysfs() to take into account device_add() failures.

This fixes CVE-2023-28464.

Link: https://syzkaller.appspot.com/bug?id=1bb51491ca5df96a5f724899d1dbb87afda61419 [1]

Signed-off-by: ZhengHan Wang <wzhmmmmm@gmail.com>
Co-developed-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---

Re-sending Luiz' version of ZhengHan Wang's patch as a reply-to snafu
caused v2 of the patch by Luiz to not be applied.

I added the CVE reference, fixed the SoB and add mention of Luiz' changes
in the commit message.

 net/bluetooth/hci_conn.c  |  6 ++----
 net/bluetooth/hci_sysfs.c | 23 ++++++++++++-----------
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 7a6f20338db8..236085451931 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -169,13 +169,11 @@ static void hci_conn_cleanup(struct hci_conn *conn)
 			hdev->notify(hdev, HCI_NOTIFY_CONN_DEL);
 	}
 
-	hci_conn_del_sysfs(conn);
-
 	debugfs_remove_recursive(conn->debugfs);
 
-	hci_dev_put(hdev);
+	hci_conn_del_sysfs(conn);
 
-	hci_conn_put(conn);
+	hci_dev_put(hdev);
 }
 
 static void hci_acl_create_connection(struct hci_conn *conn)
diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c
index 15b33579007c..367e32fe30eb 100644
--- a/net/bluetooth/hci_sysfs.c
+++ b/net/bluetooth/hci_sysfs.c
@@ -35,7 +35,7 @@ void hci_conn_init_sysfs(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
 
-	BT_DBG("conn %p", conn);
+	bt_dev_dbg(hdev, "conn %p", conn);
 
 	conn->dev.type = &bt_link;
 	conn->dev.class = &bt_class;
@@ -48,27 +48,30 @@ void hci_conn_add_sysfs(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
 
-	BT_DBG("conn %p", conn);
+	bt_dev_dbg(hdev, "conn %p", conn);
 
 	if (device_is_registered(&conn->dev))
 		return;
 
 	dev_set_name(&conn->dev, "%s:%d", hdev->name, conn->handle);
 
-	if (device_add(&conn->dev) < 0) {
+	if (device_add(&conn->dev) < 0)
 		bt_dev_err(hdev, "failed to register connection device");
-		return;
-	}
-
-	hci_dev_hold(hdev);
 }
 
 void hci_conn_del_sysfs(struct hci_conn *conn)
 {
 	struct hci_dev *hdev = conn->hdev;
 
-	if (!device_is_registered(&conn->dev))
+	bt_dev_dbg(hdev, "conn %p", conn);
+
+	if (!device_is_registered(&conn->dev)) {
+		/* If device_add() has *not* succeeded, use *only* put_device()
+		 * to drop the reference count.
+		 */
+		put_device(&conn->dev);
 		return;
+	}
 
 	while (1) {
 		struct device *dev;
@@ -80,9 +83,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn)
 		put_device(dev);
 	}
 
-	device_del(&conn->dev);
-
-	hci_dev_put(hdev);
+	device_unregister(&conn->dev);
 }
 
 static void bt_host_release(struct device *dev)
-- 
2.41.0

RE: [v3] Bluetooth: Fix double free in hci_conn_cleanup

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2805 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=794282

---Test result---

Test Summary:
CheckPatch                    FAIL      1.13 seconds
GitLint                       FAIL      0.63 seconds
SubjectPrefix                 PASS      0.12 seconds
BuildKernel                   PASS      33.67 seconds
CheckAllWarning               PASS      36.66 seconds
CheckSparse                   PASS      42.12 seconds
CheckSmatch                   PASS      113.99 seconds
BuildKernel32                 PASS      32.41 seconds
TestRunnerSetup               PASS      510.44 seconds
TestRunner_l2cap-tester       PASS      30.52 seconds
TestRunner_iso-tester         PASS      50.01 seconds
TestRunner_bnep-tester        PASS      10.43 seconds
TestRunner_mgmt-tester        PASS      216.55 seconds
TestRunner_rfcomm-tester      PASS      15.86 seconds
TestRunner_sco-tester         PASS      19.64 seconds
TestRunner_ioctl-tester       PASS      18.10 seconds
TestRunner_mesh-tester        PASS      13.59 seconds
TestRunner_smp-tester         PASS      14.38 seconds
TestRunner_userchan-tester    PASS      11.50 seconds
IncrementalBuild              PASS      33.41 seconds

Details
##############################
Test: CheckPatch - FAIL
Desc: Run checkpatch.pl script
Output:
[v3] Bluetooth: Fix double free in hci_conn_cleanup
WARNING: Co-developed-by: must be immediately followed by Signed-off-by:
#83: 
Co-developed-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
---

total: 0 errors, 1 warnings, 0 checks, 70 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

/github/workspace/src/src/13426836.patch has style problems, please review.

NOTE: Ignored message types: UNKNOWN_COMMIT_ID

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.


##############################
Test: GitLint - FAIL
Desc: Run gitlint
Output:
[v3] Bluetooth: Fix double free in hci_conn_cleanup

WARNING: I3 - ignore-body-lines: gitlint will be switching from using Python regex 'match' (match beginning) to 'search' (match anywhere) semantics. Please review your ignore-body-lines.regex option accordingly. To remove this warning, set general.regex-style-search=True. More details: https://jorisroovers.github.io/gitlint/configuration/#regex-style-search
39: B1 Line exceeds max length (87>80): "Link: https://syzkaller.appspot.com/bug?id=1bb51491ca5df96a5f724899d1dbb87afda61419 [1]"


---
Regards,
Linux Bluetooth

Re: [PATCH v3] Bluetooth: Fix double free in hci_conn_cleanup

[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, 18 Oct 2023 12:30:55 +0200 you wrote:
> From: ZhengHan Wang <wzhmmmmm@gmail.com>
> 
> syzbot reports a slab use-after-free in hci_conn_hash_flush [1].
> After releasing an object using hci_conn_del_sysfs in the
> hci_conn_cleanup function, releasing the same object again
> using the hci_dev_put and hci_conn_put functions causes a double free.
> Here's a simplified flow:
> 
> [...]

Here is the summary with links:
  - [v3] Bluetooth: Fix double free in hci_conn_cleanup
    https://git.kernel.org/bluetooth/bluetooth-next/c/4706a126c330

You are awesome, thank you!
-- 
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