Re: [syzbot] KMSAN: uninit-value in ax88178_reset

[Pavel Skripkin <paskripkin@gmail.com>]

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On 1/5/22 15:04, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    b0a8b5053e8b kmsan: core: add dependency on DEBUG_KERNEL
> git tree:       https://github.com/google/kmsan.git master
> console output: https://syzkaller.appspot.com/x/log.txt?x=159cf693b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=46a956fc7a887c60
> dashboard link: https://syzkaller.appspot.com/bug?extid=6ca9f7867b77c2d316ac
> compiler:       clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14413193b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=127716a3b00000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6ca9f7867b77c2d316ac@syzkaller.appspotmail.com
> 
> asix 1-1:0.0 eth1: Failed to read reg index 0x0000: -32
> asix 1-1:0.0 eth1: Failed to read reg index 0x0000: -32
> =====================================================
> BUG: KMSAN: uninit-value in ax88178_reset+0xfd2/0x1590 drivers/net/usb/asix_devices.c:946 drivers/net/usb/asix_devices.c:946
>   ax88178_reset+0xfd2/0x1590 drivers/net/usb/asix_devices.c:946 drivers/net/usb/asix_devices.c:946
>   usbnet_open+0x16d/0x1940 drivers/net/usb/usbnet.c:894 drivers/net/usb/usbnet.c:894
>   __dev_open+0x920/0xb90 net/core/dev.c:1490 net/core/dev.c:1490
>   __dev_change_flags+0x4da/0xd40 net/core/dev.c:8796 net/core/dev.c:8796
>   dev_change_flags+0xf5/0x280 net/core/dev.c:8867 net/core/dev.c:8867
>   devinet_ioctl+0xfc1/0x3060 net/ipv4/devinet.c:1144 net/ipv4/devinet.c:1144
>   inet_ioctl+0x59f/0x820 net/ipv4/af_inet.c:969 net/ipv4/af_inet.c:969
>   sock_do_ioctl net/socket.c:1118 [inline]
>   sock_do_ioctl net/socket.c:1118 [inline] net/socket.c:1235
>   sock_ioctl+0xa3f/0x13d0 net/socket.c:1235 net/socket.c:1235
>   vfs_ioctl fs/ioctl.c:51 [inline]
>   __do_sys_ioctl fs/ioctl.c:874 [inline]
>   vfs_ioctl fs/ioctl.c:51 [inline] fs/ioctl.c:860
>   __do_sys_ioctl fs/ioctl.c:874 [inline] fs/ioctl.c:860
>   __se_sys_ioctl+0x2df/0x4a0 fs/ioctl.c:860 fs/ioctl.c:860
>   __x64_sys_ioctl+0xd8/0x110 fs/ioctl.c:860 fs/ioctl.c:860
>   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
>   do_syscall_x64 arch/x86/entry/common.c:51 [inline] arch/x86/entry/common.c:82
>   do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 arch/x86/entry/common.c:82
>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Local variable status created at:
>   ax88178_reset+0x69/0x1590
>   usbnet_open+0x16d/0x1940 drivers/net/usb/usbnet.c:894 drivers/net/usb/usbnet.c:894

Again usbnet_read_cmd() returns 0.

It seems reasonable to mark asix_read_cmd() as __must_check, so let's do 
it and add missing error handling

#syz test: https://github.com/google/kmsan.git master



With regards,
Pavel Skripkin

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diff --git a/drivers/net/usb/asix.h b/drivers/net/usb/asix.h
index 2a1e31defe71..4334aafab59a 100644
--- a/drivers/net/usb/asix.h
+++ b/drivers/net/usb/asix.h
@@ -192,8 +192,8 @@ extern const struct driver_info ax88172a_info;
 /* ASIX specific flags */
 #define FLAG_EEPROM_MAC		(1UL << 0)  /* init device MAC from eeprom */
 
-int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
-		  u16 size, void *data, int in_pm);
+int __must_check asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
+			       u16 size, void *data, int in_pm);
 
 int asix_write_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 		   u16 size, void *data, int in_pm);
diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 71682970be58..df637d8284ab 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c
@@ -11,8 +11,8 @@
 
 #define AX_HOST_EN_RETRIES	30
 
-int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
-		  u16 size, void *data, int in_pm)
+int __must_check asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
+			       u16 size, void *data, int in_pm)
 {
 	int ret;
 	int (*fn)(struct usbnet *, u8, u8, u16, u16, void *, u16);
@@ -27,9 +27,12 @@ int asix_read_cmd(struct usbnet *dev, u8 cmd, u16 value, u16 index,
 	ret = fn(dev, cmd, USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		 value, index, data, size);
 
-	if (unlikely(ret < 0))
+	if (unlikely(ret < size)) {
+		ret = ret < 0 ? ret : -ENODATA;
+
 		netdev_warn(dev->net, "Failed to read reg index 0x%04x: %d\n",
 			    index, ret);
+	}
 
 	return ret;
 }
diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index 4514d35ef4c4..6b2fbdf4e0fd 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -755,7 +755,12 @@ static int ax88772_bind(struct usbnet *dev, struct usb_interface *intf)
 	priv->phy_addr = ret;
 	priv->embd_phy = ((priv->phy_addr & 0x1f) == 0x10);
 
-	asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG, 0, 0, 1, &chipcode, 0);
+	ret = asix_read_cmd(dev, AX_CMD_STATMNGSTS_REG, 0, 0, 1, &chipcode, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read STATMNGSTS_REG: %d\n", ret);
+		return ret;
+	}
+
 	chipcode &= AX_CHIPCODE_MASK;
 
 	ret = (chipcode == AX_AX88772_CHIPCODE) ? ax88772_hw_reset(dev, 0) :
@@ -920,11 +925,21 @@ static int ax88178_reset(struct usbnet *dev)
 	int gpio0 = 0;
 	u32 phyid;
 
-	asix_read_cmd(dev, AX_CMD_READ_GPIOS, 0, 0, 1, &status, 0);
+	ret = asix_read_cmd(dev, AX_CMD_READ_GPIOS, 0, 0, 1, &status, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read GPIOS: %d\n", ret);
+		return ret;
+	}
+
 	netdev_dbg(dev->net, "GPIO Status: 0x%04x\n", status);
 
 	asix_write_cmd(dev, AX_CMD_WRITE_ENABLE, 0, 0, 0, NULL, 0);
-	asix_read_cmd(dev, AX_CMD_READ_EEPROM, 0x0017, 0, 2, &eeprom, 0);
+	ret = asix_read_cmd(dev, AX_CMD_READ_EEPROM, 0x0017, 0, 2, &eeprom, 0);
+	if (ret < 0) {
+		netdev_dbg(dev->net, "Failed to read EEPROM: %d\n", ret);
+		return ret;
+	}
+
 	asix_write_cmd(dev, AX_CMD_WRITE_DISABLE, 0, 0, 0, NULL, 0);
 
 	netdev_dbg(dev->net, "EEPROM index 0x17 is 0x%04x\n", eeprom);