[PATCH V2] media: dvb-usb: Optimizing err() output
From: Edward Adam Davis
Date: Mon Oct 13 2025 - 20:35:42 EST
syzbot reported a uninit-value in pctv452e_i2c_msg. [1]
When the snd_len or rcv_len check fails and jumps to failed, buf is
uninitialized, triggering the uninit-value issue.
Setting the err() output buf byte count to 0 before jumping to failed
before initializing buf and setting it to 7 after initializing buf avoids
this warning.
[1]
BUG: KMSAN: uninit-value in hex_string+0x681/0x740 lib/vsprintf.c:1220
pctv452e_i2c_msg+0x82a/0x8f0 drivers/media/usb/dvb-usb/pctv452e.c:467
pctv452e_i2c_xfer+0x2e6/0x4c0 drivers/media/usb/dvb-usb/pctv452e.c:502
Reported-by: syzbot+480edd2cadb85ddb4bbe@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=480edd2cadb85ddb4bbe
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
V1 -> V2: subject typos
drivers/media/usb/dvb-usb/pctv452e.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/media/usb/dvb-usb/pctv452e.c b/drivers/media/usb/dvb-usb/pctv452e.c
index 5094de9a312e..3b6e86a8e9ff 100644
--- a/drivers/media/usb/dvb-usb/pctv452e.c
+++ b/drivers/media/usb/dvb-usb/pctv452e.c
@@ -420,7 +420,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr,
struct pctv452e_state *state = d->priv;
u8 *buf;
u8 id;
- int ret;
+ int ret, plen = 0;
buf = kmalloc(64, GFP_KERNEL);
if (!buf)
@@ -432,6 +432,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr,
if (snd_len > 64 - 7 || rcv_len > 64 - 7)
goto failed;
+ plen = 7;
buf[0] = SYNC_BYTE_OUT;
buf[1] = id;
buf[2] = PCTV_CMD_I2C;
@@ -466,7 +467,7 @@ static int pctv452e_i2c_msg(struct dvb_usb_device *d, u8 addr,
failed:
err("I2C error %d; %02X %02X %02X %02X %02X -> %*ph",
ret, SYNC_BYTE_OUT, id, addr << 1, snd_len, rcv_len,
- 7, buf);
+ plen, buf);
kfree(buf);
return ret;
--
2.43.0