[PATCH] Bluetooth: vhci: Prevent use-after-free by removing debugfs files early

[PATCH] Bluetooth: vhci: Prevent use-after-free by removing debugfs files early

[Ivan Pravdin]

Move the creation of debugfs files into a dedicated function, and ensure
they are explicitly removed during vhci_release(), before associated
data structures are freed.

Previously, debugfs files such as "force_suspend", "force_wakeup", and
others were created under hdev->debugfs but not removed in
vhci_release(). Since vhci_release() frees the backing vhci_data
structure, any access to these files after release would result in
use-after-free errors.

Although hdev->debugfs is later freed in hci_release_dev(), user can
access files after vhci_data is freed but before hdev->debugfs is
released.

Signed-off-by: Ivan Pravdin <ipravdin.official@gmail.com>
Fixes: ab4e4380d4e1 ("Bluetooth: Add vhci devcoredump support")
---
 drivers/bluetooth/hci_vhci.c | 57 ++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 16 deletions(-)

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index 59f4d7bdffdc..b72f826b2246 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -380,6 +380,28 @@ static const struct file_operations force_devcoredump_fops = {
 	.write		= force_devcd_write,
 };
 
+static void vhci_debugfs_init(struct vhci_data *data)
+{
+	struct hci_dev *hdev = data->hdev;
+
+	debugfs_create_file("force_suspend", 0644, hdev->debugfs, data,
+			    &force_suspend_fops);
+
+	debugfs_create_file("force_wakeup", 0644, hdev->debugfs, data,
+			    &force_wakeup_fops);
+
+	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
+		debugfs_create_file("msft_opcode", 0644, hdev->debugfs, data,
+				    &msft_opcode_fops);
+
+	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
+		debugfs_create_file("aosp_capable", 0644, hdev->debugfs, data,
+				    &aosp_capable_fops);
+
+	debugfs_create_file("force_devcoredump", 0644, hdev->debugfs, data,
+			    &force_devcoredump_fops);
+}
+
 static int __vhci_create_device(struct vhci_data *data, __u8 opcode)
 {
 	struct hci_dev *hdev;
@@ -434,22 +456,8 @@ static int __vhci_create_device(struct vhci_data *data, __u8 opcode)
 		return -EBUSY;
 	}
 
-	debugfs_create_file("force_suspend", 0644, hdev->debugfs, data,
-			    &force_suspend_fops);
-
-	debugfs_create_file("force_wakeup", 0644, hdev->debugfs, data,
-			    &force_wakeup_fops);
-
-	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
-		debugfs_create_file("msft_opcode", 0644, hdev->debugfs, data,
-				    &msft_opcode_fops);
-
-	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
-		debugfs_create_file("aosp_capable", 0644, hdev->debugfs, data,
-				    &aosp_capable_fops);
-
-	debugfs_create_file("force_devcoredump", 0644, hdev->debugfs, data,
-			    &force_devcoredump_fops);
+	if (!IS_ERR_OR_NULL(hdev->debugfs))
+		vhci_debugfs_init(data);
 
 	hci_skb_pkt_type(skb) = HCI_VENDOR_PKT;
 
@@ -651,6 +659,21 @@ static int vhci_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static void vhci_debugfs_remove(struct hci_dev *hdev)
+{
+	debugfs_lookup_and_remove("force_suspend", hdev->debugfs);
+
+	debugfs_lookup_and_remove("force_wakeup", hdev->debugfs);
+
+	if (IS_ENABLED(CONFIG_BT_MSFTEXT))
+		debugfs_lookup_and_remove("msft_opcode", hdev->debugfs);
+
+	if (IS_ENABLED(CONFIG_BT_AOSPEXT))
+		debugfs_lookup_and_remove("aosp_capable", hdev->debugfs);
+
+	debugfs_lookup_and_remove("force_devcoredump", hdev->debugfs);
+}
+
 static int vhci_release(struct inode *inode, struct file *file)
 {
 	struct vhci_data *data = file->private_data;
@@ -662,6 +685,8 @@ static int vhci_release(struct inode *inode, struct file *file)
 	hdev = data->hdev;
 
 	if (hdev) {
+		if (!IS_ERR_OR_NULL(hdev->debugfs))
+			vhci_debugfs_remove(hdev);
 		hci_unregister_dev(hdev);
 		hci_free_dev(hdev);
 	}
-- 
2.45.2

RE: Bluetooth: vhci: Prevent use-after-free by removing debugfs files early

[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=972172

---Test result---

Test Summary:
CheckPatch                    PENDING   0.32 seconds
GitLint                       PENDING   0.23 seconds
SubjectPrefix                 PASS      0.05 seconds
BuildKernel                   PASS      25.09 seconds
CheckAllWarning               PASS      27.22 seconds
CheckSparse                   PASS      30.76 seconds
BuildKernel32                 PASS      24.16 seconds
TestRunnerSetup               PASS      457.94 seconds
TestRunner_l2cap-tester       PASS      24.93 seconds
TestRunner_iso-tester         FAIL      7.78 seconds
TestRunner_bnep-tester        PASS      5.83 seconds
TestRunner_mgmt-tester        FAIL      131.97 seconds
TestRunner_rfcomm-tester      PASS      9.21 seconds
TestRunner_sco-tester         PASS      14.57 seconds
TestRunner_ioctl-tester       PASS      9.85 seconds
TestRunner_mesh-tester        PASS      7.27 seconds
TestRunner_smp-tester         PASS      8.36 seconds
TestRunner_userchan-tester    PASS      6.01 seconds
IncrementalBuild              PENDING   0.85 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: TestRunner_iso-tester - FAIL
Desc: Run iso-tester with test-runner
Output:
No test result found
##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 490, Passed: 485 (99.0%), Failed: 1, Not Run: 4

Failed Test Cases
LL Privacy - Set Flags 1 (Add to RL)                 Failed       0.156 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth