Bluetooth: Fix debugfs NULL pointer dereference

Fix crash caused by NULL pointer dereference when debugfs functions
le_max_key_read, le_max_key_size_write, le_min_key_size_read or
le_min_key_size_write and Bluetooth adapter was powered off.

Fix is to move max_key_size and min_key_size from smp_dev to hci_dev.
At the same time they were renamed to le_max_key_size and
le_min_key_size.

BUG: unable to handle kernel NULL pointer dereference at 00000000000002e8
PGD 0 P4D 0
Oops: 0000 [#24] SMP PTI
CPU: 2 PID: 6255 Comm: cat Tainted: G      D    OE     4.18.9-200.fc28.x86_64 #1
Hardware name: LENOVO 4286CTO/4286CTO, BIOS 8DET76WW (1.46 ) 06/21/2018
RIP: 0010:le_max_key_size_read+0x45/0xb0 [bluetooth]
Code: 00 00 00 48 83 ec 10 65 48 8b 04 25 28 00 00 00 48 89 44 24 08 31 c0 48 8b 87 c8 00 00 00 48 8d 7c 24 04 48 8b 80 48 0a 00 00 <48> 8b 80 e8 02 00 00 0f b6 48 52 e8 fb b6 b3 ed be 04 00 00 00 48
RSP: 0018:ffffab23c3ff3df0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007f0b4ca2e000 RCX: ffffab23c3ff3f08
RDX: ffffffffc0ddb033 RSI: 0000000000000004 RDI: ffffab23c3ff3df4
RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffab23c3ff3ed8 R11: 0000000000000000 R12: ffffab23c3ff3f08
R13: 00007f0b4ca2e000 R14: 0000000000020000 R15: ffffab23c3ff3f08
FS:  00007f0b4ca0f540(0000) GS:ffff91bd5e280000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000002e8 CR3: 00000000629fa006 CR4: 00000000000606e0
Call Trace:
 full_proxy_read+0x53/0x80
 __vfs_read+0x36/0x180
 vfs_read+0x8a/0x140
 ksys_read+0x4f/0xb0
 do_syscall_64+0x5b/0x160
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Matias Karhumaa <matias.karhumaa@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/hci_core.h

@@ -267,6 +267,8 @@ struct hci_dev {
 	__u16		le_max_tx_time;
 	__u16		le_max_rx_len;
 	__u16		le_max_rx_time;
+	__u8		le_max_key_size;
+	__u8		le_min_key_size;
 	__u16		discov_interleaved_timeout;
 	__u16		conn_info_min_age;
 	__u16		conn_info_max_age;

net/bluetooth/hci_core.c

@@ -3147,6 +3147,8 @@ struct hci_dev *hci_alloc_dev(void)
 	hdev->le_max_tx_time = 0x0148;
 	hdev->le_max_rx_len = 0x001b;
 	hdev->le_max_rx_time = 0x0148;
+	hdev->le_max_key_size = SMP_MAX_ENC_KEY_SIZE;
+	hdev->le_min_key_size = SMP_MIN_ENC_KEY_SIZE;
 	hdev->le_tx_def_phys = HCI_LE_SET_PHY_1M;
 	hdev->le_rx_def_phys = HCI_LE_SET_PHY_1M;
 

net/bluetooth/smp.c

@@ -88,9 +88,6 @@ struct smp_dev {
 	u8			local_rand[16];
 	bool			debug_key;
 
-	u8			min_key_size;
-	u8			max_key_size;
-
 	struct crypto_cipher	*tfm_aes;
 	struct crypto_shash	*tfm_cmac;
 	struct crypto_kpp	*tfm_ecdh;
@@ -720,7 +717,7 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 	if (rsp == NULL) {
 		req->io_capability = conn->hcon->io_capability;
 		req->oob_flag = oob_flag;
-		req->max_key_size = SMP_DEV(hdev)->max_key_size;
+		req->max_key_size = hdev->le_max_key_size;
 		req->init_key_dist = local_dist;
 		req->resp_key_dist = remote_dist;
 		req->auth_req = (authreq & AUTH_REQ_MASK(hdev));
@@ -731,7 +728,7 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 
 	rsp->io_capability = conn->hcon->io_capability;
 	rsp->oob_flag = oob_flag;
-	rsp->max_key_size = SMP_DEV(hdev)->max_key_size;
+	rsp->max_key_size = hdev->le_max_key_size;
 	rsp->init_key_dist = req->init_key_dist & remote_dist;
 	rsp->resp_key_dist = req->resp_key_dist & local_dist;
 	rsp->auth_req = (authreq & AUTH_REQ_MASK(hdev));
@@ -745,7 +742,7 @@ static u8 check_enc_key_size(struct l2cap_conn *conn, __u8 max_key_size)
 	struct hci_dev *hdev = conn->hcon->hdev;
 	struct smp_chan *smp = chan->data;
 
-	if (max_key_size > SMP_DEV(hdev)->max_key_size ||
+	if (max_key_size > hdev->le_max_key_size ||
 	    max_key_size < SMP_MIN_ENC_KEY_SIZE)
 		return SMP_ENC_KEY_SIZE;
 
@@ -3243,8 +3240,6 @@ static struct l2cap_chan *smp_add_cid(struct hci_dev *hdev, u16 cid)
 	smp->tfm_aes = tfm_aes;
 	smp->tfm_cmac = tfm_cmac;
 	smp->tfm_ecdh = tfm_ecdh;
-	smp->min_key_size = SMP_MIN_ENC_KEY_SIZE;
-	smp->max_key_size = SMP_MAX_ENC_KEY_SIZE;
 
 create_chan:
 	chan = l2cap_chan_create();
@@ -3370,7 +3365,7 @@ static ssize_t le_min_key_size_read(struct file *file,
 	struct hci_dev *hdev = file->private_data;
 	char buf[4];
 
-	snprintf(buf, sizeof(buf), "%2u\n", SMP_DEV(hdev)->min_key_size);
+	snprintf(buf, sizeof(buf), "%2u\n", hdev->le_min_key_size);
 
 	return simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf));
 }
@@ -3391,11 +3386,11 @@ static ssize_t le_min_key_size_write(struct file *file,
 
 	sscanf(buf, "%hhu", &key_size);
 
-	if (key_size > SMP_DEV(hdev)->max_key_size ||
+	if (key_size > hdev->le_max_key_size ||
 	    key_size < SMP_MIN_ENC_KEY_SIZE)
 		return -EINVAL;
 
-	SMP_DEV(hdev)->min_key_size = key_size;
+	hdev->le_min_key_size = key_size;
 
 	return count;
 }
@@ -3414,7 +3409,7 @@ static ssize_t le_max_key_size_read(struct file *file,
 	struct hci_dev *hdev = file->private_data;
 	char buf[4];
 
-	snprintf(buf, sizeof(buf), "%2u\n", SMP_DEV(hdev)->max_key_size);
+	snprintf(buf, sizeof(buf), "%2u\n", hdev->le_max_key_size);
 
 	return simple_read_from_buffer(user_buf, count, ppos, buf, strlen(buf));
 }
@@ -3436,10 +3431,10 @@ static ssize_t le_max_key_size_write(struct file *file,
 	sscanf(buf, "%hhu", &key_size);
 
 	if (key_size > SMP_MAX_ENC_KEY_SIZE ||
-	    key_size < SMP_DEV(hdev)->min_key_size)
+	    key_size < hdev->le_min_key_size)
 		return -EINVAL;
 
-	SMP_DEV(hdev)->max_key_size = key_size;
+	hdev->le_max_key_size = key_size;
 
 	return count;
 }