[PATCH] USB: sisusbvga: Change port variable from signed to unsigned

[Changming Liu <liu.changm@northeastern.edu>]

> -----Original Message-----
> From: Greg KH <greg@kroah.com>
> Sent: Monday, April 20, 2020 7:26 AM
> To: Changming Liu <liu.changm@northeastern.edu>
> Cc: thomas@winischhofer.net; linux-usb@vger.kernel.org; Lu, Long
> <l.lu@northeastern.edu>; yaohway@gmail.com
> Subject: Re: [Bug Report] drivers/usb/misc/sisusbvga: integer overflow in
> sisusb_getidxreg and others
> 
> On Sun, Apr 19, 2020 at 10:04:06PM +0000, Changming Liu wrote:
> > Hi Thomas,
> > Greetings, I'm a first-year PhD student who is interested in using
> > UBSan for linux kernel. With some experiments, I found that in
> drivers/usb/misc/sisusbvga/sisusb.c sisusb_getidxreg, there is an signed
> integer overflow which might cause unexpected result.
> >
> > More specifically, starting from the fetch function in func
> > sisusb_ioctl, line 2959, struct sisusb_command y is filled with data from user
> space. Then diving into sisusb_handle_command, the signed integer, named
> port, is casted from y->data3.
> > Then when executing sisusb_getidxreg, the signed integer, port, is used as 32-
> bit unsigned address in function sisusb_write_memio_byte.
> 
> Great, can you provide a patch fixing this so we can give you the proper credit
> for finding and fixing the issue?
Hi Greg,
Thank you very much for this recognition, this means a lot to me!
Here's the patch which I think can pretty much fix it, although I just changed the related arguments from int to u32 : p
Please feel free to modify as you like. Thanks!

Best regards,
Changming

From 6de85a157f01cb457d9c74c03769ffd7b8cf5f0e Mon Sep 17 00:00:00 2001
From: Changming Liu <liu.changm@northeastern.edu>
Date: Mon, 20 Apr 2020 23:41:25 -0400
Subject: [PATCH] USB: sisusbvga: Change port variable from signed to unsigned

Change a bunch of arguments of wrapper functions which pass signed integer to an unsigned integer
which might cause undefined behaviors when sign integer overflow.

Signed-off-by: Changming Liu <liu.changm@northeastern.edu>
---
 drivers/usb/misc/sisusbvga/sisusb.c      | 20 ++++++++++----------
 drivers/usb/misc/sisusbvga/sisusb_init.h | 14 +++++++-------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/misc/sisusbvga/sisusb.c b/drivers/usb/misc/sisusbvga/sisusb.c
index 2ab9600d0898..fc8a5da4a07c 100644
--- a/drivers/usb/misc/sisusbvga/sisusb.c
+++ b/drivers/usb/misc/sisusbvga/sisusb.c
@@ -1199,18 +1199,18 @@ static int sisusb_read_mem_bulk(struct sisusb_usb_data *sisusb, u32 addr,
 /* High level: Gfx (indexed) register access */
 
 #ifdef CONFIG_USB_SISUSBVGA_CON
-int sisusb_setreg(struct sisusb_usb_data *sisusb, int port, u8 data)
+int sisusb_setreg(struct sisusb_usb_data *sisusb, u32 port, u8 data)
 {
 	return sisusb_write_memio_byte(sisusb, SISUSB_TYPE_IO, port, data);
 }
 
-int sisusb_getreg(struct sisusb_usb_data *sisusb, int port, u8 *data)
+int sisusb_getreg(struct sisusb_usb_data *sisusb, u32 port, u8 *data)
 {
 	return sisusb_read_memio_byte(sisusb, SISUSB_TYPE_IO, port, data);
 }
 #endif
 
-int sisusb_setidxreg(struct sisusb_usb_data *sisusb, int port,
+int sisusb_setidxreg(struct sisusb_usb_data *sisusb, u32 port,
 		u8 index, u8 data)
 {
 	int ret;
@@ -1220,7 +1220,7 @@ int sisusb_setidxreg(struct sisusb_usb_data *sisusb, int port,
 	return ret;
 }
 
-int sisusb_getidxreg(struct sisusb_usb_data *sisusb, int port,
+int sisusb_getidxreg(struct sisusb_usb_data *sisusb, u32 port,
 		u8 index, u8 *data)
 {
 	int ret;
@@ -1230,7 +1230,7 @@ int sisusb_getidxreg(struct sisusb_usb_data *sisusb, int port,
 	return ret;
 }
 
-int sisusb_setidxregandor(struct sisusb_usb_data *sisusb, int port, u8 idx,
+int sisusb_setidxregandor(struct sisusb_usb_data *sisusb, u32 port, u8 idx,
 		u8 myand, u8 myor)
 {
 	int ret;
@@ -1245,7 +1245,7 @@ int sisusb_setidxregandor(struct sisusb_usb_data *sisusb, int port, u8 idx,
 }
 
 static int sisusb_setidxregmask(struct sisusb_usb_data *sisusb,
-		int port, u8 idx, u8 data, u8 mask)
+		u32 port, u8 idx, u8 data, u8 mask)
 {
 	int ret;
 	u8 tmp;
@@ -1258,13 +1258,13 @@ static int sisusb_setidxregmask(struct sisusb_usb_data *sisusb,
 	return ret;
 }
 
-int sisusb_setidxregor(struct sisusb_usb_data *sisusb, int port,
+int sisusb_setidxregor(struct sisusb_usb_data *sisusb, u32 port,
 		u8 index, u8 myor)
 {
 	return sisusb_setidxregandor(sisusb, port, index, 0xff, myor);
 }
 
-int sisusb_setidxregand(struct sisusb_usb_data *sisusb, int port,
+int sisusb_setidxregand(struct sisusb_usb_data *sisusb, u32 port,
 		u8 idx, u8 myand)
 {
 	return sisusb_setidxregandor(sisusb, port, idx, myand, 0x00);
@@ -2785,8 +2785,8 @@ static loff_t sisusb_lseek(struct file *file, loff_t offset, int orig)
 static int sisusb_handle_command(struct sisusb_usb_data *sisusb,
 		struct sisusb_command *y, unsigned long arg)
 {
-	int	retval, port, length;
-	u32	address;
+	int	retval, length;
+	u32	port, address;
 
 	/* All our commands require the device
 	 * to be initialized.
diff --git a/drivers/usb/misc/sisusbvga/sisusb_init.h b/drivers/usb/misc/sisusbvga/sisusb_init.h
index 1782c759c4ad..ace09985dae4 100644
--- a/drivers/usb/misc/sisusbvga/sisusb_init.h
+++ b/drivers/usb/misc/sisusbvga/sisusb_init.h
@@ -812,17 +812,17 @@ static const struct SiS_VCLKData SiSUSB_VCLKData[] = {
 int SiSUSBSetMode(struct SiS_Private *SiS_Pr, unsigned short ModeNo);
 int SiSUSBSetVESAMode(struct SiS_Private *SiS_Pr, unsigned short VModeNo);
 
-extern int sisusb_setreg(struct sisusb_usb_data *sisusb, int port, u8 data);
-extern int sisusb_getreg(struct sisusb_usb_data *sisusb, int port, u8 * data);
-extern int sisusb_setidxreg(struct sisusb_usb_data *sisusb, int port,
+extern int sisusb_setreg(struct sisusb_usb_data *sisusb, u32 port, u8 data);
+extern int sisusb_getreg(struct sisusb_usb_data *sisusb, u32 port, u8 * data);
+extern int sisusb_setidxreg(struct sisusb_usb_data *sisusb, u32 port,
 			    u8 index, u8 data);
-extern int sisusb_getidxreg(struct sisusb_usb_data *sisusb, int port,
+extern int sisusb_getidxreg(struct sisusb_usb_data *sisusb, u32 port,
 			    u8 index, u8 * data);
-extern int sisusb_setidxregandor(struct sisusb_usb_data *sisusb, int port,
+extern int sisusb_setidxregandor(struct sisusb_usb_data *sisusb, u32 port,
 				 u8 idx, u8 myand, u8 myor);
-extern int sisusb_setidxregor(struct sisusb_usb_data *sisusb, int port,
+extern int sisusb_setidxregor(struct sisusb_usb_data *sisusb, u32 port,
 			      u8 index, u8 myor);
-extern int sisusb_setidxregand(struct sisusb_usb_data *sisusb, int port,
+extern int sisusb_setidxregand(struct sisusb_usb_data *sisusb, u32 port,
 			       u8 idx, u8 myand);
 
 void sisusb_delete(struct kref *kref);
-- 
2.17.1

> 
> thanks,
> 
> greg k-h