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Date:   Mon, 2 Aug 2021 23:07:23 +0300
From:   Petko Manolov <petkan@...leusys.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+02c9f70f3afae308464a@...kaller.appspotmail.com
Subject: Re: [PATCH] net: pegasus: fix uninit-value in get_interrupt_interval

On 21-08-01 22:35:13, Pavel Skripkin wrote:
> On Sun, 1 Aug 2021 15:36:27 +0300
> Petko Manolov <petkan@...leusys.com> wrote:
> 
> > On 21-07-31 00:44:11, Pavel Skripkin wrote:
> > > Syzbot reported uninit value pegasus_probe(). The problem was in missing
> > > error handling.
> > > 
> > > get_interrupt_interval() internally calls read_eprom_word() which can fail
> > > in some cases. For example: failed to receive usb control message. These
> > > cases should be handled to prevent uninit value bug, since
> > > read_eprom_word() will not initialize passed stack variable in case of
> > > internal failure.
> > 
> > Well, this is most definitelly a bug.
> > 
> > ACK!
> > 
> > 
> > 		Petko
> > 
> > 
> 
> Thank you, Petko!
> 
> 
> BTW: I found a lot uses of {get,set}_registers without error checking. I
> think, some of them could be fixed easily (like in enable_eprom_write), but, I
> guess, disable_eprom_write is not so easy. For example, if we cannot disable
> eprom should we retry? If not, will device get in some unexpected state?
> 
> Im not familiar with this device, but I can prepare a patch to wrap all these
> calls with proper error checking

Here goes a preliminary patch that should apply on top of your, maybe with just
a few warnings.  This is a review only diff, not the real patch.  It's against
5.14-rc4.

I am mildly curious why syzbot didn't catch the same type of bug in
enable_net_traffic() and setup_pegasus_II() for example.


		Petko

---

diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c
index 9a907182569c..eafbe8107907 100644
--- a/drivers/net/usb/pegasus.c
+++ b/drivers/net/usb/pegasus.c
@@ -26,6 +26,8 @@
  *		...
  *		v0.9.3	simplified [get|set]_register(s), async update registers
  *			logic revisited, receive skb_pool removed.
+ *		v1.0.1	add error checking for set_register(s)(), see if calling
+ *			get_registers() has failed and print a message accordingly.
  */
 
 #include <linux/sched.h>
@@ -45,7 +47,7 @@
 /*
  * Version Information
  */
-#define DRIVER_VERSION "v0.9.3 (2013/04/25)"
+#define DRIVER_VERSION "v1.0.1 (2021/08/01)"
 #define DRIVER_AUTHOR "Petko Manolov <petkan@...leusys.com>"
 #define DRIVER_DESC "Pegasus/Pegasus II USB Ethernet driver"
 
@@ -132,9 +134,15 @@ static int get_registers(pegasus_t *pegasus, __u16 indx, __u16 size, void *data)
 static int set_registers(pegasus_t *pegasus, __u16 indx, __u16 size,
 			 const void *data)
 {
-	return usb_control_msg_send(pegasus->usb, 0, PEGASUS_REQ_SET_REGS,
+	int ret;
+
+	ret = usb_control_msg_send(pegasus->usb, 0, PEGASUS_REQ_SET_REGS,
 				    PEGASUS_REQT_WRITE, 0, indx, data, size,
 				    1000, GFP_NOIO);
+	if (ret < 0)
+		netif_dbg(pegasus, drv, pegasus->net, "%s failed with %d\n", __func__, ret);
+
+	return ret;
 }
 
 /*
@@ -145,10 +153,15 @@ static int set_registers(pegasus_t *pegasus, __u16 indx, __u16 size,
 static int set_register(pegasus_t *pegasus, __u16 indx, __u8 data)
 {
 	void *buf = &data;
+	int ret;
 
-	return usb_control_msg_send(pegasus->usb, 0, PEGASUS_REQ_SET_REG,
+	ret = usb_control_msg_send(pegasus->usb, 0, PEGASUS_REQ_SET_REG,
 				    PEGASUS_REQT_WRITE, data, indx, buf, 1,
 				    1000, GFP_NOIO);
+	if (ret < 0)
+		netif_dbg(pegasus, drv, pegasus->net, "%s failed with %d\n", __func__, ret);
+
+	return ret;
 }
 
 static int update_eth_regs_async(pegasus_t *pegasus)
@@ -188,10 +201,9 @@ static int update_eth_regs_async(pegasus_t *pegasus)
 
 static int __mii_op(pegasus_t *p, __u8 phy, __u8 indx, __u16 *regd, __u8 cmd)
 {
-	int i;
-	__u8 data[4] = { phy, 0, 0, indx };
+	int i, ret = -ETIMEDOUT;
 	__le16 regdi;
-	int ret = -ETIMEDOUT;
+	__u8 data[4] = { phy, 0, 0, indx };
 
 	if (cmd & PHY_WRITE) {
 		__le16 *t = (__le16 *) & data[1];
@@ -211,8 +223,9 @@ static int __mii_op(pegasus_t *p, __u8 phy, __u8 indx, __u16 *regd, __u8 cmd)
 		goto fail;
 	if (cmd & PHY_READ) {
 		ret = get_registers(p, PhyData, 2, &regdi);
+		if (ret < 0)
+			goto fail;
 		*regd = le16_to_cpu(regdi);
-		return ret;
 	}
 	return 0;
 fail:
@@ -235,9 +248,13 @@ static int write_mii_word(pegasus_t *pegasus, __u8 phy, __u8 indx, __u16 *regd)
 static int mdio_read(struct net_device *dev, int phy_id, int loc)
 {
 	pegasus_t *pegasus = netdev_priv(dev);
+	int ret;
 	u16 res;
 
-	read_mii_word(pegasus, phy_id, loc, &res);
+	ret = read_mii_word(pegasus, phy_id, loc, &res);
+	if (ret < 0)
+		return ret;
+
 	return (int)res;
 }
 
@@ -251,10 +268,9 @@ static void mdio_write(struct net_device *dev, int phy_id, int loc, int val)
 
 static int read_eprom_word(pegasus_t *pegasus, __u8 index, __u16 *retdata)
 {
-	int i;
-	__u8 tmp = 0;
+	int ret, i;
 	__le16 retdatai;
-	int ret;
+	__u8 tmp = 0;
 
 	set_register(pegasus, EpromCtrl, 0);
 	set_register(pegasus, EpromOffset, index);
@@ -262,21 +278,25 @@ static int read_eprom_word(pegasus_t *pegasus, __u8 index, __u16 *retdata)
 
 	for (i = 0; i < REG_TIMEOUT; i++) {
 		ret = get_registers(pegasus, EpromCtrl, 1, &tmp);
+		if (ret < 0)
+			goto fail;
 		if (tmp & EPROM_DONE)
 			break;
-		if (ret == -ESHUTDOWN)
-			goto fail;
 	}
-	if (i >= REG_TIMEOUT)
+	if (i >= REG_TIMEOUT) {
+		ret = -ETIMEDOUT;
 		goto fail;
+	}
 
 	ret = get_registers(pegasus, EpromData, 2, &retdatai);
+	if (ret < 0)
+		goto fail;
 	*retdata = le16_to_cpu(retdatai);
 	return ret;
 
 fail:
-	netif_warn(pegasus, drv, pegasus->net, "%s failed\n", __func__);
-	return -ETIMEDOUT;
+	netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
+	return ret;
 }
 
 #ifdef	PEGASUS_WRITE_EEPROM
@@ -324,10 +344,10 @@ static int write_eprom_word(pegasus_t *pegasus, __u8 index, __u16 data)
 	return ret;
 
 fail:
-	netif_warn(pegasus, drv, pegasus->net, "%s failed\n", __func__);
+	netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
 	return -ETIMEDOUT;
 }
-#endif				/* PEGASUS_WRITE_EEPROM */
+#endif	/* PEGASUS_WRITE_EEPROM */
 
 static inline int get_node_id(pegasus_t *pegasus, u8 *id)
 {
@@ -367,19 +387,21 @@ static void set_ethernet_addr(pegasus_t *pegasus)
 	return;
 err:
 	eth_hw_addr_random(pegasus->net);
-	dev_info(&pegasus->intf->dev, "software assigned MAC address.\n");
+	netif_dbg(pegasus, drv, pegasus->net, "software assigned MAC address.\n");
 
 	return;
 }
 
 static inline int reset_mac(pegasus_t *pegasus)
 {
+	int ret, i;
 	__u8 data = 0x8;
-	int i;
 
 	set_register(pegasus, EthCtrl1, data);
 	for (i = 0; i < REG_TIMEOUT; i++) {
-		get_registers(pegasus, EthCtrl1, 1, &data);
+		ret = get_registers(pegasus, EthCtrl1, 1, &data);
+		if (ret < 0)
+			goto fail;
 		if (~data & 0x08) {
 			if (loopback)
 				break;
@@ -402,22 +424,29 @@ static inline int reset_mac(pegasus_t *pegasus)
 	}
 	if (usb_dev_id[pegasus->dev_index].vendor == VENDOR_ELCON) {
 		__u16 auxmode;
-		read_mii_word(pegasus, 3, 0x1b, &auxmode);
+		ret = read_mii_word(pegasus, 3, 0x1b, &auxmode);
+		if (ret < 0)
+			goto fail;
 		auxmode |= 4;
 		write_mii_word(pegasus, 3, 0x1b, &auxmode);
 	}
 
 	return 0;
+fail:
+	netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
+	return ret;
 }
 
 static int enable_net_traffic(struct net_device *dev, struct usb_device *usb)
 {
-	__u16 linkpart;
-	__u8 data[4];
 	pegasus_t *pegasus = netdev_priv(dev);
 	int ret;
+	__u16 linkpart;
+	__u8 data[4];
 
-	read_mii_word(pegasus, pegasus->phy, MII_LPA, &linkpart);
+	ret = read_mii_word(pegasus, pegasus->phy, MII_LPA, &linkpart);
+	if (ret < 0)
+		goto fail;
 	data[0] = 0xc8; /* TX & RX enable, append status, no CRC */
 	data[1] = 0;
 	if (linkpart & (ADVERTISE_100FULL | ADVERTISE_10FULL))
@@ -435,11 +464,16 @@ static int enable_net_traffic(struct net_device *dev, struct usb_device *usb)
 	    usb_dev_id[pegasus->dev_index].vendor == VENDOR_LINKSYS2 ||
 	    usb_dev_id[pegasus->dev_index].vendor == VENDOR_DLINK) {
 		u16 auxmode;
-		read_mii_word(pegasus, 0, 0x1b, &auxmode);
+		ret = read_mii_word(pegasus, 0, 0x1b, &auxmode);
+		if (ret < 0)
+			goto fail;
 		auxmode |= 4;
 		write_mii_word(pegasus, 0, 0x1b, &auxmode);
 	}
 
+	return 0;
+fail:
+	netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
 	return ret;
 }
 
@@ -447,9 +481,9 @@ static void read_bulk_callback(struct urb *urb)
 {
 	pegasus_t *pegasus = urb->context;
 	struct net_device *net;
+	u8 *buf = urb->transfer_buffer;
 	int rx_status, count = urb->actual_length;
 	int status = urb->status;
-	u8 *buf = urb->transfer_buffer;
 	__u16 pkt_len;
 
 	if (!pegasus)
@@ -1049,6 +1083,7 @@ static __u8 mii_phy_probe(pegasus_t *pegasus)
 
 static inline void setup_pegasus_II(pegasus_t *pegasus)
 {
+	int ret;
 	__u8 data = 0xa5;
 
 	set_register(pegasus, Reg1d, 0);
@@ -1060,7 +1095,9 @@ static inline void setup_pegasus_II(pegasus_t *pegasus)
 		set_register(pegasus, Reg7b, 2);
 
 	set_register(pegasus, 0x83, data);
-	get_registers(pegasus, 0x83, 1, &data);
+	ret = get_registers(pegasus, 0x83, 1, &data);
+	if (ret < 0)
+		goto fail;
 
 	if (data == 0xa5)
 		pegasus->chip = 0x8513;
@@ -1075,6 +1112,8 @@ static inline void setup_pegasus_II(pegasus_t *pegasus)
 		set_register(pegasus, Reg81, 6);
 	else
 		set_register(pegasus, Reg81, 2);
+fail:
+	netif_dbg(pegasus, drv, pegasus->net, "%s failed\n", __func__);
 }
 
 static void check_carrier(struct work_struct *work)

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