[PATCH v3 0/3] staging: rtl8712: fix KMSAN: uninit-value in r871xu_drv_init

[PATCH v3 0/3] staging: rtl8712: fix KMSAN: uninit-value in r871xu_drv_init

[Wang Cheng]

Changelog v2->v3:
- Add error handler in r8712_usbctrl_vendorreq().

v2: https://lore.kernel.org/lkml/cover.1651760402.git.wanngchenng@gmail.com/

Wang Cheng (3):
  staging: rtl8712: fix uninit-value in usb_read8() and friends
  staging: rtl8712: fix uninit-value in r871xu_drv_init()
  staging: rtl8712: add error handler in r8712_usbctrl_vendorreq()

 drivers/staging/rtl8712/usb_intf.c      |  6 +++---
 drivers/staging/rtl8712/usb_ops.c       | 27 ++++++++++++++++---------
 drivers/staging/rtl8712/usb_ops_linux.c | 21 ++++++++++++-------
 3 files changed, 35 insertions(+), 19 deletions(-)

-- 
2.33.1

[PATCH v3 1/3] staging: rtl8712: fix uninit-value in usb_read8() and friends

[Wang Cheng]

When r8712_usbctrl_vendorreq() returns negative, 'data' in
usb_read{8,16,32} will not be initialized.

BUG: KMSAN: uninit-value in string_nocheck lib/vsprintf.c:643 [inline]
BUG: KMSAN: uninit-value in string+0x4ec/0x6f0 lib/vsprintf.c:725
 string_nocheck lib/vsprintf.c:643 [inline]
 string+0x4ec/0x6f0 lib/vsprintf.c:725
 vsnprintf+0x2222/0x3650 lib/vsprintf.c:2806
 va_format lib/vsprintf.c:1704 [inline]
 pointer+0x18e6/0x1f70 lib/vsprintf.c:2443
 vsnprintf+0x1a9b/0x3650 lib/vsprintf.c:2810
 vprintk_store+0x537/0x2150 kernel/printk/printk.c:2158
 vprintk_emit+0x28b/0xab0 kernel/printk/printk.c:2256
 dev_vprintk_emit+0x5ef/0x6d0 drivers/base/core.c:4604
 dev_printk_emit+0x1dd/0x21f drivers/base/core.c:4615
 __dev_printk+0x3be/0x440 drivers/base/core.c:4627
 _dev_info+0x1ea/0x22f drivers/base/core.c:4673
 r871xu_drv_init+0x1929/0x3070 drivers/staging/rtl8712/usb_intf.c:401
 usb_probe_interface+0xf19/0x1600 drivers/usb/core/driver.c:396
 really_probe+0x6c7/0x1350 drivers/base/dd.c:621
 __driver_probe_device+0x3e9/0x530 drivers/base/dd.c:752
 driver_probe_device drivers/base/dd.c:782 [inline]
 __device_attach_driver+0x79f/0x1120 drivers/base/dd.c:899
 bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427
 __device_attach+0x593/0x8e0 drivers/base/dd.c:970
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:1017
 bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487
 device_add+0x1fff/0x26e0 drivers/base/core.c:3405
 usb_set_configuration+0x37e9/0x3ed0 drivers/usb/core/message.c:2170
 usb_generic_driver_probe+0x13c/0x300 drivers/usb/core/generic.c:238
 usb_probe_device+0x309/0x570 drivers/usb/core/driver.c:293
 really_probe+0x6c7/0x1350 drivers/base/dd.c:621
 __driver_probe_device+0x3e9/0x530 drivers/base/dd.c:752
 driver_probe_device drivers/base/dd.c:782 [inline]
 __device_attach_driver+0x79f/0x1120 drivers/base/dd.c:899
 bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427
 __device_attach+0x593/0x8e0 drivers/base/dd.c:970
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:1017
 bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487
 device_add+0x1fff/0x26e0 drivers/base/core.c:3405
 usb_new_device+0x1b91/0x2950 drivers/usb/core/hub.c:2566
 hub_port_connect drivers/usb/core/hub.c:5363 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5507 [inline]
 port_event drivers/usb/core/hub.c:5665 [inline]
 hub_event+0x58e3/0x89e0 drivers/usb/core/hub.c:5747
 process_one_work+0xdb6/0x1820 kernel/workqueue.c:2289
 worker_thread+0x10d0/0x2240 kernel/workqueue.c:2436
 kthread+0x3c7/0x500 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

Local variable data created at:
 usb_read8+0x5d/0x130 drivers/staging/rtl8712/usb_ops.c:33
 r8712_read8+0xa5/0xd0 drivers/staging/rtl8712/rtl8712_io.c:29

Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
---
 drivers/staging/rtl8712/usb_ops.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/drivers/staging/rtl8712/usb_ops.c b/drivers/staging/rtl8712/usb_ops.c
index e64845e6adf3..af9966d03979 100644
--- a/drivers/staging/rtl8712/usb_ops.c
+++ b/drivers/staging/rtl8712/usb_ops.c
@@ -29,7 +29,8 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
 	u16 wvalue;
 	u16 index;
 	u16 len;
-	__le32 data;
+	int status;
+	__le32 data = 0;
 	struct intf_priv *intfpriv = intfhdl->pintfpriv;
 
 	request = 0x05;
@@ -37,8 +38,10 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
 	index = 0;
 	wvalue = (u16)(addr & 0x0000ffff);
 	len = 1;
-	r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len,
-				requesttype);
+	status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
+					 &data, len, requesttype);
+	if (status < 0)
+		return 0;
 	return (u8)(le32_to_cpu(data) & 0x0ff);
 }
 
@@ -49,7 +52,8 @@ static u16 usb_read16(struct intf_hdl *intfhdl, u32 addr)
 	u16 wvalue;
 	u16 index;
 	u16 len;
-	__le32 data;
+	int status;
+	__le32 data = 0;
 	struct intf_priv *intfpriv = intfhdl->pintfpriv;
 
 	request = 0x05;
@@ -57,8 +61,10 @@ static u16 usb_read16(struct intf_hdl *intfhdl, u32 addr)
 	index = 0;
 	wvalue = (u16)(addr & 0x0000ffff);
 	len = 2;
-	r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len,
-				requesttype);
+	status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
+					 &data, len, requesttype);
+	if (status < 0)
+		return 0;
 	return (u16)(le32_to_cpu(data) & 0xffff);
 }
 
@@ -69,7 +75,8 @@ static u32 usb_read32(struct intf_hdl *intfhdl, u32 addr)
 	u16 wvalue;
 	u16 index;
 	u16 len;
-	__le32 data;
+	int status;
+	__le32 data = 0;
 	struct intf_priv *intfpriv = intfhdl->pintfpriv;
 
 	request = 0x05;
@@ -77,8 +84,10 @@ static u32 usb_read32(struct intf_hdl *intfhdl, u32 addr)
 	index = 0;
 	wvalue = (u16)(addr & 0x0000ffff);
 	len = 4;
-	r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len,
-				requesttype);
+	status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
+					 &data, len, requesttype);
+	if (status < 0)
+		return 0;
 	return le32_to_cpu(data);
 }
 
-- 
2.33.1

[PATCH v3 2/3] staging: rtl8712: fix uninit-value in r871xu_drv_init()

[Wang Cheng]

When 'tmpU1b' returns from r8712_read8(padapter, EE_9346CR) is 0,
'mac[6]' will not be initialized.

BUG: KMSAN: uninit-value in r871xu_drv_init+0x2d54/0x3070 drivers/staging/rtl8712/usb_intf.c:541
 r871xu_drv_init+0x2d54/0x3070 drivers/staging/rtl8712/usb_intf.c:541
 usb_probe_interface+0xf19/0x1600 drivers/usb/core/driver.c:396
 really_probe+0x653/0x14b0 drivers/base/dd.c:596
 __driver_probe_device+0x3e9/0x530 drivers/base/dd.c:752
 driver_probe_device drivers/base/dd.c:782 [inline]
 __device_attach_driver+0x79f/0x1120 drivers/base/dd.c:899
 bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427
 __device_attach+0x593/0x8e0 drivers/base/dd.c:970
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:1017
 bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487
 device_add+0x1fff/0x26e0 drivers/base/core.c:3405
 usb_set_configuration+0x37e9/0x3ed0 drivers/usb/core/message.c:2170
 usb_generic_driver_probe+0x13c/0x300 drivers/usb/core/generic.c:238
 usb_probe_device+0x309/0x570 drivers/usb/core/driver.c:293
 really_probe+0x653/0x14b0 drivers/base/dd.c:596
 __driver_probe_device+0x3e9/0x530 drivers/base/dd.c:752
 driver_probe_device drivers/base/dd.c:782 [inline]
 __device_attach_driver+0x79f/0x1120 drivers/base/dd.c:899
 bus_for_each_drv+0x2d6/0x3f0 drivers/base/bus.c:427
 __device_attach+0x593/0x8e0 drivers/base/dd.c:970
 device_initial_probe+0x4a/0x60 drivers/base/dd.c:1017
 bus_probe_device+0x17b/0x3e0 drivers/base/bus.c:487
 device_add+0x1fff/0x26e0 drivers/base/core.c:3405
 usb_new_device+0x1b8e/0x2950 drivers/usb/core/hub.c:2566
 hub_port_connect drivers/usb/core/hub.c:5358 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5502 [inline]
 port_event drivers/usb/core/hub.c:5660 [inline]
 hub_event+0x58e3/0x89e0 drivers/usb/core/hub.c:5742
 process_one_work+0xdb6/0x1820 kernel/workqueue.c:2307
 worker_thread+0x10b3/0x21e0 kernel/workqueue.c:2454
 kthread+0x3c7/0x500 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30

Local variable mac created at:
 r871xu_drv_init+0x1771/0x3070 drivers/staging/rtl8712/usb_intf.c:394
 usb_probe_interface+0xf19/0x1600 drivers/usb/core/driver.c:396

Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
---
 drivers/staging/rtl8712/usb_intf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
index ee4c61f85a07..50dcd3ecb685 100644
--- a/drivers/staging/rtl8712/usb_intf.c
+++ b/drivers/staging/rtl8712/usb_intf.c
@@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
 		} else {
 			AutoloadFail = false;
 		}
-		if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
+		if ((!AutoloadFail) ||
+		    ((mac[0] == 0xff) && (mac[1] == 0xff) &&
 		     (mac[2] == 0xff) && (mac[3] == 0xff) &&
 		     (mac[4] == 0xff) && (mac[5] == 0xff)) ||
 		    ((mac[0] == 0x00) && (mac[1] == 0x00) &&
 		     (mac[2] == 0x00) && (mac[3] == 0x00) &&
-		     (mac[4] == 0x00) && (mac[5] == 0x00)) ||
-		     (!AutoloadFail)) {
+		     (mac[4] == 0x00) && (mac[5] == 0x00))) {
 			mac[0] = 0x00;
 			mac[1] = 0xe0;
 			mac[2] = 0x4c;
-- 
2.33.1

[PATCH v3 3/3] staging: rtl8712: add error handler in r8712_usbctrl_vendorreq()

[Wang Cheng]

When 'status' returned from usb_control_msg() is not equal to 'len',
that usb_control_msg() is on partial failure, r8712_usbctrl_vendorreq()
will treat partial reads as success.

Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
---
 drivers/staging/rtl8712/usb_ops_linux.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/rtl8712/usb_ops_linux.c b/drivers/staging/rtl8712/usb_ops_linux.c
index f984a5ab2c6f..b2181e1e2d38 100644
--- a/drivers/staging/rtl8712/usb_ops_linux.c
+++ b/drivers/staging/rtl8712/usb_ops_linux.c
@@ -495,14 +495,21 @@ int r8712_usbctrl_vendorreq(struct intf_priv *pintfpriv, u8 request, u16 value,
 	}
 	status = usb_control_msg(udev, pipe, request, reqtype, value, index,
 				 pIo_buf, len, 500);
-	if (status > 0) {  /* Success this control transfer. */
-		if (requesttype == 0x01) {
-			/* For Control read transfer, we have to copy the read
-			 * data from pIo_buf to pdata.
-			 */
-			memcpy(pdata, pIo_buf,  status);
-		}
+	if (status < 0)
+		goto free;
+	if (status != len) {
+		status = -EREMOTEIO;
+		goto free;
+	}
+	/* Success this control transfer. */
+	if (requesttype == 0x01) {
+		/* For Control read transfer, we have to copy the read
+		 * data from pIo_buf to pdata.
+		 */
+		memcpy(pdata, pIo_buf, status);
 	}
+
+free:
 	kfree(palloc_buf);
 	return status;
 }
-- 
2.33.1

Re: [PATCH v3 1/3] staging: rtl8712: fix uninit-value in usb_read8() and friends

[Pavel Skripkin]

[-- Attachment #1.1: Type: text/plain, Size: 2021 bytes --]

Hi Wang,

On 5/6/22 14:59, Wang Cheng wrote:
> Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
> Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
> ---
>   drivers/staging/rtl8712/usb_ops.c | 27 ++++++++++++++++++---------
>   1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/rtl8712/usb_ops.c b/drivers/staging/rtl8712/usb_ops.c
> index e64845e6adf3..af9966d03979 100644
> --- a/drivers/staging/rtl8712/usb_ops.c
> +++ b/drivers/staging/rtl8712/usb_ops.c
> @@ -29,7 +29,8 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
>   	u16 wvalue;
>   	u16 index;
>   	u16 len;
> -	__le32 data;
> +	int status;
> +	__le32 data = 0;
>   	struct intf_priv *intfpriv = intfhdl->pintfpriv;
>   
>   	request = 0x05;
> @@ -37,8 +38,10 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
>   	index = 0;
>   	wvalue = (u16)(addr & 0x0000ffff);
>   	len = 1;
> -	r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len,
> -				requesttype);
> +	status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
> +					 &data, len, requesttype);
> +	if (status < 0)
> +		return 0;

Wait, but what about partial reads? I see that r8712_usbctrl_vendorreq() 
uses `usb_control_msg()` which can read less data than was requested.

So here you are just hiding these error by zeroing data

>   	return (u8)(le32_to_cpu(data) & 0x0ff);
>   }
>   

And as i said in previous email: caller can't see an error.

Imagine caller waits for some register to become 0. Caller sees that 
usb_read8() returned 0. Is it an error? Is register really become 0?


Generic read API prototype looks like following:

int read_something(struct my_cool_dev *dev, void *data, size_t size);

and it returns 0 on success and -errno on failure and data returned via 
passed pointer. So, if API returned an error caller should not touch 
@data, since likely it's uninitialized




With regards,
Pavel Skripkin

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Re: [PATCH v3 3/3] staging: rtl8712: add error handler in r8712_usbctrl_vendorreq()

[Pavel Skripkin]

[-- Attachment #1.1: Type: text/plain, Size: 1677 bytes --]

Hi Wang,

On 5/6/22 15:01, Wang Cheng wrote:
> When 'status' returned from usb_control_msg() is not equal to 'len',
> that usb_control_msg() is on partial failure, r8712_usbctrl_vendorreq()
> will treat partial reads as success.
> 
> Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
> ---
>   drivers/staging/rtl8712/usb_ops_linux.c | 21 ++++++++++++++-------
>   1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/rtl8712/usb_ops_linux.c b/drivers/staging/rtl8712/usb_ops_linux.c
> index f984a5ab2c6f..b2181e1e2d38 100644
> --- a/drivers/staging/rtl8712/usb_ops_linux.c
> +++ b/drivers/staging/rtl8712/usb_ops_linux.c
> @@ -495,14 +495,21 @@ int r8712_usbctrl_vendorreq(struct intf_priv *pintfpriv, u8 request, u16 value,
>   	}
>   	status = usb_control_msg(udev, pipe, request, reqtype, value, index,
>   				 pIo_buf, len, 500);
> -	if (status > 0) {  /* Success this control transfer. */
> -		if (requesttype == 0x01) {
> -			/* For Control read transfer, we have to copy the read
> -			 * data from pIo_buf to pdata.
> -			 */
> -			memcpy(pdata, pIo_buf,  status);
> -		}
> +	if (status < 0)
> +		goto free;
> +	if (status != len) {
> +		status = -EREMOTEIO;
> +		goto free;
> +	}
> +	/* Success this control transfer. */
> +	if (requesttype == 0x01) {
> +		/* For Control read transfer, we have to copy the read
> +		 * data from pIo_buf to pdata.
> +		 */
> +		memcpy(pdata, pIo_buf, status);
>   	}
> +
> +free:
>   	kfree(palloc_buf);
>   	return status;
>   }

Ah, here it is. This patch should be 1st in the series, since 1/3 now 
looks buggy.




With regards,
Pavel Skripkin

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Re: [PATCH v3 2/3] staging: rtl8712: fix uninit-value in r871xu_drv_init()

[Pavel Skripkin]

[-- Attachment #1.1: Type: text/plain, Size: 1747 bytes --]

Hi Wang,

On 5/6/22 14:59, Wang Cheng wrote:
> Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
> Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
> ---
>   drivers/staging/rtl8712/usb_intf.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
> index ee4c61f85a07..50dcd3ecb685 100644
> --- a/drivers/staging/rtl8712/usb_intf.c
> +++ b/drivers/staging/rtl8712/usb_intf.c
> @@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
>   		} else {
>   			AutoloadFail = false;
>   		}
> -		if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
> +		if ((!AutoloadFail) ||
> +		    ((mac[0] == 0xff) && (mac[1] == 0xff) &&
>   		     (mac[2] == 0xff) && (mac[3] == 0xff) &&
>   		     (mac[4] == 0xff) && (mac[5] == 0xff)) ||
>   		    ((mac[0] == 0x00) && (mac[1] == 0x00) &&
>   		     (mac[2] == 0x00) && (mac[3] == 0x00) &&
> -		     (mac[4] == 0x00) && (mac[5] == 0x00)) ||
> -		     (!AutoloadFail)) {
> +		     (mac[4] == 0x00) && (mac[5] == 0x00))) {
>   			mac[0] = 0x00;
>   			mac[1] = 0xe0;
>   			mac[2] = 0x4c;

Hmm,

the whole r871xu_drv_init() looks odd, but it's unrelated.

I see that this patch does not help with below kernel path

r871xu_drv_init()
   if (tmpU1b & _EEPROM_EN) <- true [1]
	if (!r8712_initmac || !mac_pton(r8712_initmac, mac)) <- (*)
		if ((!AutoloadFail) ||	<- false, since [1] branch taken
			[code touches stack data]

(*) false because of r8712_initmac is equal to NULL


I saw, that syzbot said OK on your patch, but it's because you have just 
hided an error inside read API



With regards,
Pavel Skripkin

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Re: [PATCH v3 2/3] staging: rtl8712: fix uninit-value in r871xu_drv_init()

[Pavel Skripkin]

[-- Attachment #1.1: Type: text/plain, Size: 1884 bytes --]

Hi Pavel,

On 5/6/22 15:27, Pavel Skripkin wrote:
> Hi Wang,
> 
> On 5/6/22 14:59, Wang Cheng wrote:
>> Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
>> Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
>> ---
>>   drivers/staging/rtl8712/usb_intf.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
>> index ee4c61f85a07..50dcd3ecb685 100644
>> --- a/drivers/staging/rtl8712/usb_intf.c
>> +++ b/drivers/staging/rtl8712/usb_intf.c
>> @@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
>>   		} else {
>>   			AutoloadFail = false;
>>   		}
>> -		if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
>> +		if ((!AutoloadFail) ||
>> +		    ((mac[0] == 0xff) && (mac[1] == 0xff) &&
>>   		     (mac[2] == 0xff) && (mac[3] == 0xff) &&
>>   		     (mac[4] == 0xff) && (mac[5] == 0xff)) ||
>>   		    ((mac[0] == 0x00) && (mac[1] == 0x00) &&
>>   		     (mac[2] == 0x00) && (mac[3] == 0x00) &&
>> -		     (mac[4] == 0x00) && (mac[5] == 0x00)) ||
>> -		     (!AutoloadFail)) {
>> +		     (mac[4] == 0x00) && (mac[5] == 0x00))) {
>>   			mac[0] = 0x00;
>>   			mac[1] = 0xe0;
>>   			mac[2] = 0x4c;
> 
> Hmm,
> 
> the whole r871xu_drv_init() looks odd, but it's unrelated.
> 
> I see that this patch does not help with below kernel path
> 
> r871xu_drv_init()
>     if (tmpU1b & _EEPROM_EN) <- true [1]
> 	if (!r8712_initmac || !mac_pton(r8712_initmac, mac)) <- (*)
> 		if ((!AutoloadFail) ||	<- false, since [1] branch taken
> 			[code touches stack data]
> 
> (*) false because of r8712_initmac is equal to NULL
> 

Oops, I am blind, ignore that one, please. The whole idea is wrong.

I need to go to sleep earlier today

sorry about that,


With regards,
Pavel Skripkin

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Re: [PATCH v3 1/3] staging: rtl8712: fix uninit-value in usb_read8() and friends

[Wang Cheng]

On 22/05/06 03:12PM, Pavel Skripkin wrote:
> Hi Wang,
> 
> On 5/6/22 14:59, Wang Cheng wrote:
> > Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@syzkaller.appspotmail.com
> > Signed-off-by: Wang Cheng <wanngchenng@gmail.com>
> > ---
> >   drivers/staging/rtl8712/usb_ops.c | 27 ++++++++++++++++++---------
> >   1 file changed, 18 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/staging/rtl8712/usb_ops.c b/drivers/staging/rtl8712/usb_ops.c
> > index e64845e6adf3..af9966d03979 100644
> > --- a/drivers/staging/rtl8712/usb_ops.c
> > +++ b/drivers/staging/rtl8712/usb_ops.c
> > @@ -29,7 +29,8 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
> >   	u16 wvalue;
> >   	u16 index;
> >   	u16 len;
> > -	__le32 data;
> > +	int status;
> > +	__le32 data = 0;
> >   	struct intf_priv *intfpriv = intfhdl->pintfpriv;
> >   	request = 0x05;
> > @@ -37,8 +38,10 @@ static u8 usb_read8(struct intf_hdl *intfhdl, u32 addr)
> >   	index = 0;
> >   	wvalue = (u16)(addr & 0x0000ffff);
> >   	len = 1;
> > -	r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index, &data, len,
> > -				requesttype);
> > +	status = r8712_usbctrl_vendorreq(intfpriv, request, wvalue, index,
> > +					 &data, len, requesttype);
> > +	if (status < 0)
> > +		return 0;
> 
> Wait, but what about partial reads? I see that r8712_usbctrl_vendorreq()
> uses `usb_control_msg()` which can read less data than was requested.
> 
> So here you are just hiding these error by zeroing data
> 
> >   	return (u8)(le32_to_cpu(data) & 0x0ff);
> >   }
> 
> And as i said in previous email: caller can't see an error.
> 
> Imagine caller waits for some register to become 0. Caller sees that
> usb_read8() returned 0. Is it an error? Is register really become 0?
> 
> 
> Generic read API prototype looks like following:
> 
> int read_something(struct my_cool_dev *dev, void *data, size_t size);
> 
> and it returns 0 on success and -errno on failure and data returned via
> passed pointer. So, if API returned an error caller should not touch @data,
> since likely it's uninitialized

Thank you for your remind, sorry I didnt understand your previous reply
about "register and 0" that you explain very clearly above. I am thinking
about it standing on that the return type of usb_read8() is u8.

thanks,
- w