[PATCH AUTOSEL 5.11 018/104] i2c: bail out early when RDWR parameters are wrong

From: Sasha Levin
Date: Wed May 05 2021 - 12:47:50 EST


From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>

[ Upstream commit 71581562ee36032d2d574a9b23ad4af6d6a64cf7 ]

The buggy parameters currently get caught later, but emit a noisy WARN.
Userspace should not be able to trigger this, so add similar checks much
earlier. Also avoids some unneeded code paths, of course. Apply kernel
coding stlye to a comment while here.

Reported-by: syzbot+ffb0b3ffa6cfbc7d7b3f@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+ffb0b3ffa6cfbc7d7b3f@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/i2c/i2c-dev.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 6ceb11cc4be1..6ef38a8ee95c 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -440,8 +440,13 @@ static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
sizeof(rdwr_arg)))
return -EFAULT;

- /* Put an arbitrary limit on the number of messages that can
- * be sent at once */
+ if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+ return -EINVAL;
+
+ /*
+ * Put an arbitrary limit on the number of messages that can
+ * be sent at once
+ */
if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
return -EINVAL;

--
2.30.2