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Subject[PATCH v3] i2c: validate user data in compat ioctl
Date
Wrong user data may cause warning in i2c_transfer(), ex: zero msgs.
Userspace should not be able to trigger warnings, so this patch adds
validation checks for user data in compact ioctl to prevent reported
warnings

Reported-and-tested-by: syzbot+e417648b303855b91d8a@syzkaller.appspotmail.com
Fixes: 7d5cb45655f2 ("i2c compat ioctls: move to ->compat_ioctl()")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---

Changes in v3
- Add rdwr_arg.nmsgs == 0 check as Wolfram suggested

Changes in v2:
- Fixed typos in commit message

---
drivers/i2c/i2c-dev.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index bce0e8bb7852..cf5d049342ea 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -535,6 +535,9 @@ static long compat_i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned lo
sizeof(rdwr_arg)))
return -EFAULT;

+ if (!rdwr_arg.msgs || rdwr_arg.nmsgs == 0)
+ return -EINVAL;
+
if (rdwr_arg.nmsgs > I2C_RDWR_IOCTL_MAX_MSGS)
return -EINVAL;

--
2.34.1
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