linux-kernel - Re: [PATCH] i2c: dev: Fix memory leak when underlying adapter does not support I2C

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Message-ID: <Zy1Xvk9YKrjqc4S7@google.com>
Date: Fri, 8 Nov 2024 00:13:50 +0000
From: Igor Pylypiv <ipylypiv@...gle.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Jean Delvare <jdelvare@...e.de>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: dev: Fix memory leak when underlying adapter does
 not support I2C

On Thu, Nov 07, 2024 at 06:14:29PM +0100, Andi Shyti wrote:
> Hi Igor,
> 
> that's a good catch, but...
> 
> On Thu, Nov 07, 2024 at 01:48:27AM +0000, Igor Pylypiv wrote:
> > i2cdev_ioctl_rdwr() receives a buffer which is allocated by the caller.
> 
> This needs to be a bit re-written. In the commit log you should
> describe what the patch does. You are telling where the buffer is
> allocated.

I thought subject line covered what the patch does. Ack. I'll update
the commit message in v2.

> 
> > Fixes: 97ca843f6ad3 ("i2c: dev: Check for I2C_FUNC_I2C before calling i2c_transfer")
> > Signed-off-by: Igor Pylypiv <ipylypiv@...gle.com>
> > ---
> >  drivers/i2c/i2c-dev.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
> > index 61f7c4003d2f..5d15519ef737 100644
> > --- a/drivers/i2c/i2c-dev.c
> > +++ b/drivers/i2c/i2c-dev.c
> > @@ -247,8 +247,10 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
> >  	int i, res;
> >  
> >  	/* Adapter must support I2C transfers */
> > -	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
> > +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
> > +		kfree(msgs);
> >  		return -EOPNOTSUPP;
> 
> Please, don't free it here, free it where it has been allocated,
> i.e. in compat_i2cdev_ioctl().
>

Sounds good. I'll move kfree() in v2.

Thanks,
Igor
 
> Andi
> 
> > +	}
> >  
> >  	data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
> >  	if (data_ptrs == NULL) {
> > -- 
> > 2.47.0.277.g8800431eea-goog
> >