xhci: fix even more unsafe memory usage in xhci tracing

Removes static char buffer usage in the following decode functions:
	xhci_decode_ctrl_ctx()
	xhci_decode_slot_context()
	xhci_decode_usbsts()
	xhci_decode_doorbell()
	xhci_decode_ep_context()

Caller must provide a buffer to use.
In tracing use __get_str() as recommended to pass buffer.

Minor changes are needed in other xhci code as these functions are also
used elsewhere

Cc: <stable@vger.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210820123503.2605901-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-debugfs.c

@@ -261,11 +261,13 @@ static int xhci_slot_context_show(struct seq_file *s, void *unused)
 	struct xhci_slot_ctx	*slot_ctx;
 	struct xhci_slot_priv	*priv = s->private;
 	struct xhci_virt_device	*dev = priv->dev;
+	char			str[XHCI_MSG_MAX];
 
 	xhci = hcd_to_xhci(bus_to_hcd(dev->udev->bus));
 	slot_ctx = xhci_get_slot_ctx(xhci, dev->out_ctx);
 	seq_printf(s, "%pad: %s\n", &dev->out_ctx->dma,
-		   xhci_decode_slot_context(le32_to_cpu(slot_ctx->dev_info),
+		   xhci_decode_slot_context(str,
+					    le32_to_cpu(slot_ctx->dev_info),
 					    le32_to_cpu(slot_ctx->dev_info2),
 					    le32_to_cpu(slot_ctx->tt_info),
 					    le32_to_cpu(slot_ctx->dev_state)));
@@ -281,14 +283,16 @@ static int xhci_endpoint_context_show(struct seq_file *s, void *unused)
 	struct xhci_ep_ctx	*ep_ctx;
 	struct xhci_slot_priv	*priv = s->private;
 	struct xhci_virt_device	*dev = priv->dev;
+	char			str[XHCI_MSG_MAX];
 
 	xhci = hcd_to_xhci(bus_to_hcd(dev->udev->bus));
 
 	for (ep_index = 0; ep_index < 31; ep_index++) {
 		ep_ctx = xhci_get_ep_ctx(xhci, dev->out_ctx, ep_index);
 		dma = dev->out_ctx->dma + (ep_index + 1) * CTX_SIZE(xhci->hcc_params);
 		seq_printf(s, "%pad: %s\n", &dma,
-			   xhci_decode_ep_context(le32_to_cpu(ep_ctx->ep_info),
+			   xhci_decode_ep_context(str,
+						  le32_to_cpu(ep_ctx->ep_info),
 						  le32_to_cpu(ep_ctx->ep_info2),
 						  le64_to_cpu(ep_ctx->deq),
 						  le32_to_cpu(ep_ctx->tx_info)));

drivers/usb/host/xhci-ring.c

@@ -1212,6 +1212,7 @@ void xhci_stop_endpoint_command_watchdog(struct timer_list *t)
 	struct xhci_hcd *xhci = ep->xhci;
 	unsigned long flags;
 	u32 usbsts;
+	char str[XHCI_MSG_MAX];
 
 	spin_lock_irqsave(&xhci->lock, flags);
 
@@ -1225,7 +1226,7 @@ void xhci_stop_endpoint_command_watchdog(struct timer_list *t)
 	usbsts = readl(&xhci->op_regs->status);
 
 	xhci_warn(xhci, "xHCI host not responding to stop endpoint command.\n");
-	xhci_warn(xhci, "USBSTS:%s\n", xhci_decode_usbsts(usbsts));
+	xhci_warn(xhci, "USBSTS:%s\n", xhci_decode_usbsts(str, usbsts));
 
 	ep->ep_state &= ~EP_STOP_CMD_PENDING;
 

drivers/usb/host/xhci-trace.h

@@ -322,15 +322,16 @@ DECLARE_EVENT_CLASS(xhci_log_ep_ctx,
 		__field(u32, info2)
 		__field(u64, deq)
 		__field(u32, tx_info)
+		__dynamic_array(char, str, XHCI_MSG_MAX)
 	),
 	TP_fast_assign(
 		__entry->info = le32_to_cpu(ctx->ep_info);
 		__entry->info2 = le32_to_cpu(ctx->ep_info2);
 		__entry->deq = le64_to_cpu(ctx->deq);
 		__entry->tx_info = le32_to_cpu(ctx->tx_info);
 	),
-	TP_printk("%s", xhci_decode_ep_context(__entry->info,
-		__entry->info2, __entry->deq, __entry->tx_info)
+	TP_printk("%s", xhci_decode_ep_context(__get_str(str),
+		__entry->info, __entry->info2, __entry->deq, __entry->tx_info)
 	)
 );
 
@@ -367,16 +368,17 @@ DECLARE_EVENT_CLASS(xhci_log_slot_ctx,
 		__field(u32, info2)
 		__field(u32, tt_info)
 		__field(u32, state)
+		__dynamic_array(char, str, XHCI_MSG_MAX)
 	),
 	TP_fast_assign(
 		__entry->info = le32_to_cpu(ctx->dev_info);
 		__entry->info2 = le32_to_cpu(ctx->dev_info2);
 		__entry->tt_info = le64_to_cpu(ctx->tt_info);
 		__entry->state = le32_to_cpu(ctx->dev_state);
 	),
-	TP_printk("%s", xhci_decode_slot_context(__entry->info,
-			__entry->info2, __entry->tt_info,
-			__entry->state)
+	TP_printk("%s", xhci_decode_slot_context(__get_str(str),
+			__entry->info, __entry->info2,
+			__entry->tt_info, __entry->state)
 	)
 );
 
@@ -431,12 +433,13 @@ DECLARE_EVENT_CLASS(xhci_log_ctrl_ctx,
 	TP_STRUCT__entry(
 		__field(u32, drop)
 		__field(u32, add)
+		__dynamic_array(char, str, XHCI_MSG_MAX)
 	),
 	TP_fast_assign(
 		__entry->drop = le32_to_cpu(ctrl_ctx->drop_flags);
 		__entry->add = le32_to_cpu(ctrl_ctx->add_flags);
 	),
-	TP_printk("%s", xhci_decode_ctrl_ctx(__entry->drop, __entry->add)
+	TP_printk("%s", xhci_decode_ctrl_ctx(__get_str(str), __entry->drop, __entry->add)
 	)
 );
 
@@ -555,13 +558,14 @@ DECLARE_EVENT_CLASS(xhci_log_doorbell,
 	TP_STRUCT__entry(
 		__field(u32, slot)
 		__field(u32, doorbell)
+		__dynamic_array(char, str, XHCI_MSG_MAX)
 	),
 	TP_fast_assign(
 		__entry->slot = slot;
 		__entry->doorbell = doorbell;
 	),
 	TP_printk("Ring doorbell for %s",
-		xhci_decode_doorbell(__entry->slot, __entry->doorbell)
+		  xhci_decode_doorbell(__get_str(str), __entry->slot, __entry->doorbell)
 	)
 );
 

drivers/usb/host/xhci.h

@@ -2460,10 +2460,9 @@ static inline const char *xhci_decode_trb(char *str, size_t size,
 	return str;
 }
 
-static inline const char *xhci_decode_ctrl_ctx(unsigned long drop,
-					       unsigned long add)
+static inline const char *xhci_decode_ctrl_ctx(char *str,
+		unsigned long drop, unsigned long add)
 {
-	static char	str[1024];
 	unsigned int	bit;
 	int		ret = 0;
 
@@ -2489,10 +2488,9 @@ static inline const char *xhci_decode_ctrl_ctx(unsigned long drop,
 	return str;
 }
 
-static inline const char *xhci_decode_slot_context(u32 info, u32 info2,
-		u32 tt_info, u32 state)
+static inline const char *xhci_decode_slot_context(char *str,
+		u32 info, u32 info2, u32 tt_info, u32 state)
 {
-	static char str[1024];
 	u32 speed;
 	u32 hub;
 	u32 mtt;
@@ -2621,9 +2619,8 @@ static inline const char *xhci_decode_portsc(char *str, u32 portsc)
 	return str;
 }
 
-static inline const char *xhci_decode_usbsts(u32 usbsts)
+static inline const char *xhci_decode_usbsts(char *str, u32 usbsts)
 {
-	static char str[256];
 	int ret = 0;
 
 	if (usbsts == ~(u32)0)
@@ -2650,9 +2647,8 @@ static inline const char *xhci_decode_usbsts(u32 usbsts)
 	return str;
 }
 
-static inline const char *xhci_decode_doorbell(u32 slot, u32 doorbell)
+static inline const char *xhci_decode_doorbell(char *str, u32 slot, u32 doorbell)
 {
-	static char str[256];
 	u8 ep;
 	u16 stream;
 	int ret;
@@ -2719,10 +2715,9 @@ static inline const char *xhci_ep_type_string(u8 type)
 	}
 }
 
-static inline const char *xhci_decode_ep_context(u32 info, u32 info2, u64 deq,
-		u32 tx_info)
+static inline const char *xhci_decode_ep_context(char *str, u32 info,
+		u32 info2, u64 deq, u32 tx_info)
 {
-	static char str[1024];
 	int ret;
 
 	u32 esit;