[PATCH v2 1/2] asix: fix uninit-value in asix_mdio_read()

asix_read_cmd() may read less than sizeof(smsr) bytes and in this case
smsr will be uninitialized.

Fail log:
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
BUG: KMSAN: uninit-value in asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
 asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497

Fixes: d9fe64e51114 ("net: asix: Add in_pm parameter")
Reported-and-tested-by: syzbot+f44badb06036334e867a@syzkaller.appspotmail.com
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Pavel Skripkin <redacted>
---

Changes in v2:
	- Added Reviewed-by tag

---
 drivers/net/usb/asix_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 42ba4af68090..06823d7141b6 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c

@@ -77,7 +77,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 				    0, 0, 1, &smsr, in_pm);
 		if (ret == -ENODEV)
 			break;
-		else if (ret < 0)
+		else if (ret < sizeof(smsr))
 			continue;
 		else if (smsr & AX_HOST_EN)
 			break;

-- 
2.34.1

If asix_read_cmd() returns 0 on 30th interation, 0 will be returned from
asix_check_host_enable(), which is logically wrong. Fix it by returning
-ETIMEDOUT explicitly if we have exceeded 30 iterations

Also, replaced 30 with #define as suggested by Andrew

Fixes: a786e3195d6a ("net: asix: fix uninit value bugs")
Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Pavel Skripkin <redacted>
---

Changes in v2:
	- Fixed coding style issues
	- Replaced 30 with #define

---
 drivers/net/usb/asix_common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/asix_common.c b/drivers/net/usb/asix_common.c
index 06823d7141b6..71682970be58 100644
--- a/drivers/net/usb/asix_common.c
+++ b/drivers/net/usb/asix_common.c

@@ -9,6 +9,8 @@
 
 #include "asix.h"
 
+#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)
 {

@@ -68,7 +70,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 	int i, ret;
 	u8 smsr;
 
-	for (i = 0; i < 30; ++i) {
+	for (i = 0; i < AX_HOST_EN_RETRIES; ++i) {
 		ret = asix_set_sw_mii(dev, in_pm);
 		if (ret == -ENODEV || ret == -ETIMEDOUT)
 			break;

@@ -83,7 +85,7 @@ static int asix_check_host_enable(struct usbnet *dev, int in_pm)
 			break;
 	}
 
-	return ret;
+	return i >= AX_HOST_EN_RETRIES ? -ETIMEDOUT : ret;
 }
 
 static void reset_asix_rx_fixup_info(struct asix_rx_fixup_info *rx)

-- 
2.34.1

On Tue, Dec 21, 2021 at 11:10:43PM +0300, Pavel Skripkin wrote:

If asix_read_cmd() returns 0 on 30th interation, 0 will be returned from
asix_check_host_enable(), which is logically wrong. Fix it by returning
-ETIMEDOUT explicitly if we have exceeded 30 iterations

Also, replaced 30 with #define as suggested by Andrew

Fixes: a786e3195d6a ("net: asix: fix uninit value bugs")
Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Pavel Skripkin <redacted>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

Hello:

This series was applied to netdev/net.git (master)
by Jakub Kicinski [off-list ref]:

On Tue, 21 Dec 2021 23:10:36 +0300 you wrote:

asix_read_cmd() may read less than sizeof(smsr) bytes and in this case
smsr will be uninitialized.

Fail log:
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
BUG: KMSAN: uninit-value in asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
BUG: KMSAN: uninit-value in asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline]
 asix_check_host_enable drivers/net/usb/asix_common.c:82 [inline] drivers/net/usb/asix_common.c:497
 asix_mdio_read+0x3c1/0xb00 drivers/net/usb/asix_common.c:497 drivers/net/usb/asix_common.c:497

[...]

Here is the summary with links:
  - [v2,1/2] asix: fix uninit-value in asix_mdio_read()
    https://git.kernel.org/netdev/net/c/8035b1a2a37a
  - [v2,2/2] asix: fix wrong return value in asix_check_host_enable()
    https://git.kernel.org/netdev/net/c/d1652b70d07c

You are awesome, thank you!
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