usb: hub: Guard against accesses to uninitialized BOS descriptors

Many functions in drivers/usb/core/hub.c and drivers/usb/core/hub.h
access fields inside udev->bos without checking if it was allocated and
initialized. If usb_get_bos_descriptor() fails for whatever
reason, udev->bos will be NULL and those accesses will result in a
crash:

BUG: kernel NULL pointer dereference, address: 0000000000000018
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 5 PID: 17818 Comm: kworker/5:1 Tainted: G W 5.15.108-18910-gab0e1cb584e1 #1 <HASH:1f9e 1>
Hardware name: Google Kindred/Kindred, BIOS Google_Kindred.12672.413.0 02/03/2021
Workqueue: usb_hub_wq hub_event
RIP: 0010:hub_port_reset+0x193/0x788
Code: 89 f7 e8 20 f7 15 00 48 8b 43 08 80 b8 96 03 00 00 03 75 36 0f b7 88 92 03 00 00 81 f9 10 03 00 00 72 27 48 8b 80 a8 03 00 00 <48> 83 78 18 00 74 19 48 89 df 48 8b 75 b0 ba 02 00 00 00 4c 89 e9
RSP: 0018:ffffab740c53fcf8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffa1bc5f678000 RCX: 0000000000000310
RDX: fffffffffffffdff RSI: 0000000000000286 RDI: ffffa1be9655b840
RBP: ffffab740c53fd70 R08: 00001b7d5edaa20c R09: ffffffffb005e060
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: ffffab740c53fd3e R14: 0000000000000032 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffffa1be96540000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000018 CR3: 000000022e80c005 CR4: 00000000003706e0
Call Trace:
hub_event+0x73f/0x156e
? hub_activate+0x5b7/0x68f
process_one_work+0x1a2/0x487
worker_thread+0x11a/0x288
kthread+0x13a/0x152
? process_one_work+0x487/0x487
? kthread_associate_blkcg+0x70/0x70
ret_from_fork+0x1f/0x30

Fall back to a default behavior if the BOS descriptor isn't accessible
and skip all the functionalities that depend on it: LPM support checks,
Super Speed capabilitiy checks, U1/U2 states setup.

Signed-off-by: Ricardo Cañuelo <ricardo.canuelo@collabora.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20230830100418.1952143-1-ricardo.canuelo@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: r-c-n

drivers/usb/core/hub.c

@@ -151,6 +151,10 @@ int usb_device_supports_lpm(struct usb_device *udev)
 	if (udev->quirks & USB_QUIRK_NO_LPM)
 		return 0;
 
+	/* Skip if the device BOS descriptor couldn't be read */
+	if (!udev->bos)
+		return 0;
+
 	/* USB 2.1 (and greater) devices indicate LPM support through
 	 * their USB 2.0 Extended Capabilities BOS descriptor.
 	 */
@@ -327,6 +331,10 @@ static void usb_set_lpm_parameters(struct usb_device *udev)
 	if (!udev->lpm_capable || udev->speed < USB_SPEED_SUPER)
 		return;
 
+	/* Skip if the device BOS descriptor couldn't be read */
+	if (!udev->bos)
+		return;
+
 	hub = usb_hub_to_struct_hub(udev->parent);
 	/* It doesn't take time to transition the roothub into U0, since it
 	 * doesn't have an upstream link.
@@ -2704,13 +2712,17 @@ int usb_authorize_device(struct usb_device *usb_dev)
 static enum usb_ssp_rate get_port_ssp_rate(struct usb_device *hdev,
 					   u32 ext_portstatus)
 {
-	struct usb_ssp_cap_descriptor *ssp_cap = hdev->bos->ssp_cap;
+	struct usb_ssp_cap_descriptor *ssp_cap;
 	u32 attr;
 	u8 speed_id;
 	u8 ssac;
 	u8 lanes;
 	int i;
 
+	if (!hdev->bos)
+		goto out;
+
+	ssp_cap = hdev->bos->ssp_cap;
 	if (!ssp_cap)
 		goto out;
 
@@ -4215,8 +4227,15 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev,
 		enum usb3_link_state state)
 {
 	int timeout;
-	__u8 u1_mel = udev->bos->ss_cap->bU1devExitLat;
-	__le16 u2_mel = udev->bos->ss_cap->bU2DevExitLat;
+	__u8 u1_mel;
+	__le16 u2_mel;
+
+	/* Skip if the device BOS descriptor couldn't be read */
+	if (!udev->bos)
+		return;
+
+	u1_mel = udev->bos->ss_cap->bU1devExitLat;
+	u2_mel = udev->bos->ss_cap->bU2DevExitLat;
 
 	/* If the device says it doesn't have *any* exit latency to come out of
 	 * U1 or U2, it's probably lying.  Assume it doesn't implement that link

drivers/usb/core/hub.h

@@ -153,7 +153,7 @@ static inline int hub_is_superspeedplus(struct usb_device *hdev)
 {
 	return (hdev->descriptor.bDeviceProtocol == USB_HUB_PR_SS &&
 		le16_to_cpu(hdev->descriptor.bcdUSB) >= 0x0310 &&
-		hdev->bos->ssp_cap);
+		hdev->bos && hdev->bos->ssp_cap);
 }
 
 static inline unsigned hub_power_on_good_delay(struct usb_hub *hub)