[PATCH] i2c: bail out early when RDWR parameters are wrong

* [PATCH] i2c: bail out early when RDWR parameters are wrong
@ 2021-03-12 11:57 Wolfram Sang
  2021-03-18 11:15 ` Wolfram Sang
  0 siblings, 1 reply; 2+ messages in thread
From: Wolfram Sang @ 2021-03-12 11:57 UTC (permalink / raw)
  To: linux-i2c; +Cc: Wolfram Sang, syzbot+ffb0b3ffa6cfbc7d7b3f

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@syzkaller.appspotmail.com
Tested-by: syzbot+ffb0b3ffa6cfbc7d7b3f@syzkaller.appspotmail.com
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 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;
 
-- 
2.30.0


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