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From:   Alexandru Ardelean <ardeleanalex@gmail.com>
Date:   Mon, 18 Oct 2021 10:03:25 +0300
Message-ID: <CA+U=DspGn7m8wz=a3Dr6VdD57DNc=+tS-fGZmr7m_JcEYADwdg@mail.gmail.com>
Subject: Re: [PATCH] iio: buffer: Fix memory leak in __iio_buffer_alloc_sysfs_and_mask()
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     Yang Yingliang <yangyingliang@huawei.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>
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On Sun, Oct 17, 2021 at 5:12 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Wed, 13 Oct 2021 17:43:43 +0800
> Yang Yingliang <yangyingliang@huawei.com> wrote:
>
> > When iio_buffer_wrap_attr() returns NULL or buffer->buffer_group.name alloc
> > fails, the 'attr' which is allocated in __iio_buffer_alloc_sysfs_and_mask()
> > is not freed, and cause memory leak.
> >
> > unreferenced object 0xffff888014882a00 (size 64):
> >   comm "i2c-adjd_s311-8", pid 424, jiffies 4294907737 (age 44.396s)
> >   hex dump (first 32 bytes):
> >     00 0f 8a 15 80 88 ff ff 00 0e 8a 15 80 88 ff ff  ................
> >     80 04 8a 15 80 88 ff ff 80 05 8a 15 80 88 ff ff  ................
> >   backtrace:
> >     [<0000000021752e67>] __kmalloc+0x1af/0x3c0
> >     [<0000000043e8305c>] iio_buffers_alloc_sysfs_and_mask+0xe73/0x1570 [industrialio]
> >     [<00000000b7aa5a17>] __iio_device_register+0x483/0x1a30 [industrialio]
> >     [<000000003fa0fb2f>] __devm_iio_device_register+0x23/0x90 [industrialio]
> >     [<000000003ab040cf>] adjd_s311_probe+0x19c/0x200 [adjd_s311]
> >     [<0000000080458969>] i2c_device_probe+0xa31/0xbe0
> >     [<00000000e20678ad>] really_probe+0x299/0xc30
> >     [<000000006bea9b27>] __driver_probe_device+0x357/0x500
> >     [<00000000e1df10d4>] driver_probe_device+0x4e/0x140
> >     [<0000000003661beb>] __device_attach_driver+0x257/0x340
> >     [<000000005bb4aa26>] bus_for_each_drv+0x166/0x1e0
> >     [<00000000272c5236>] __device_attach+0x272/0x420
> >     [<00000000d52a96ae>] bus_probe_device+0x1eb/0x2a0
> >     [<00000000129f7737>] device_add+0xbf0/0x1f90
> >     [<000000005eed4e52>] i2c_new_client_device+0x622/0xb20
> >     [<00000000b85a9c43>] new_device_store+0x1fa/0x420
> >
> > This patch fix to free it before the error return.
> >
> > Reported-by: Hulk Robot <hulkci@huawei.com>
> > Fixes: 15097c7a1adc ("iio: buffer: wrap all buffer attributes into iio_dev_attr")
> > Fixes: d9a625744ed0 ("iio: core: merge buffer/ & scan_elements/ attributes")
> > Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
>
> Good find.  This function is clearly trying to do too many things and hence has become
> rather error prone.  Still fixing that is a job for another day.
>
> Alex, if you have a chance to take a look at this as well it would be great.
> In the meantime I've queued it up in the fixes-togreg branch of iio.git

Yeah, this fix looks good.
It took me a while to follow the change.

No need to add my tag [anywhere] since this was sent already.

Looking at all these leak fixes coming in, I'm wondering where my head
was at, when doing these changes.

Thanks
Alex

>
> Thanks,
>
> Jonathan
>
> > ---
> >  drivers/iio/industrialio-buffer.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> > index 547a92d469ae..ae0912a14578 100644
> > --- a/drivers/iio/industrialio-buffer.c
> > +++ b/drivers/iio/industrialio-buffer.c
> > @@ -1536,6 +1536,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> >                      sizeof(struct attribute *) * buffer_attrcount);
> >
> >       buffer_attrcount += ARRAY_SIZE(iio_buffer_attrs);
> > +     buffer->buffer_group.attrs = attr;
> >
> >       for (i = 0; i < buffer_attrcount; i++) {
> >               struct attribute *wrapped;
> > @@ -1543,7 +1544,7 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> >               wrapped = iio_buffer_wrap_attr(buffer, attr[i]);
> >               if (!wrapped) {
> >                       ret = -ENOMEM;
> > -                     goto error_free_scan_mask;
> > +                     goto error_free_buffer_attrs;
> >               }
> >               attr[i] = wrapped;
> >       }
> > @@ -1558,8 +1559,6 @@ static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
> >               goto error_free_buffer_attrs;
> >       }
> >
> > -     buffer->buffer_group.attrs = attr;
> > -
> >       ret = iio_device_register_sysfs_group(indio_dev, &buffer->buffer_group);
> >       if (ret)
> >               goto error_free_buffer_attr_group_name;
>