From: Lars-Peter Clausen <lars@metafoo.de>
To: Peter Meerwald <pmeerw@pmeerw.net>
Cc: linux-iio@vger.kernel.org
Subject: Re: [PATCH 2/2] iio: Fix crash when scan_bytes is computed with active_scan_mask == NULL
Date: Thu, 19 Sep 2013 08:48:45 +0200 [thread overview]
Message-ID: <523A9E4D.9010208@metafoo.de> (raw)
In-Reply-To: <1379538649-9675-2-git-send-email-pmeerw@pmeerw.net>
On 09/18/2013 11:10 PM, Peter Meerwald wrote:
> if device has available_scan_masks set and the buffer is enabled without
> any scan_elements enabled, in a NULL pointer is dereferenced in iio_compute_scan_bytes()
>
> [ 18.993713] Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [ 19.002593] pgd = debd4000
> [ 19.005432] [00000000] *pgd=9ebc0831, *pte=00000000, *ppte=00000000
> [ 19.012329] Internal error: Oops: 17 [#1] PREEMPT ARM
> [ 19.017639] Modules linked in:
> [ 19.020843] CPU: 0 Not tainted (3.9.11-00036-g75c888a-dirty #207)
> [ 19.027587] PC is at _find_first_bit_le+0xc/0x2c
> [ 19.032440] LR is at iio_compute_scan_bytes+0x2c/0xf4
> [ 19.037719] pc : [<c021dc60>] lr : [<c03198d0>] psr: 200d0013
> [ 19.037719] sp : debd9ed0 ip : 00000000 fp : 000802bc
> [ 19.049713] r10: 00000000 r9 : 00000000 r8 : deb67250
> [ 19.055206] r7 : 00000000 r6 : 00000000 r5 : 00000000 r4 : deb67000
> [ 19.062011] r3 : de96ec00 r2 : 00000000 r1 : 00000004 r0 : 00000000
> [ 19.068847] Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
> [ 19.076324] Control: 10c5387d Table: 9ebd4019 DAC: 00000015
>
> problem is the rollback code in iio_update_buffers(), old_mask may be NULL (e.g. on first
> call)
>
> I'm not too confident about the fix; works for me...
Looks good. We should probably try to restructure the function at some point as
it is quite hard to follow as it is right now.
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
>
> Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
> ---
> drivers/iio/industrialio-buffer.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 2361fbc..d5754b8 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -522,8 +522,15 @@ int iio_update_buffers(struct iio_dev *indio_dev,
> * Note can only occur when adding a buffer.
> */
> list_del_init(&insert_buffer->buffer_list);
> - indio_dev->active_scan_mask = old_mask;
> - success = -EINVAL;
> + if (old_mask) {
> + indio_dev->active_scan_mask = old_mask;
> + success = -EINVAL;
> + }
> + else {
> + kfree(compound_mask);
> + ret = -EINVAL;
> + goto error_ret;
> + }
> }
> } else {
> indio_dev->active_scan_mask = compound_mask;
>
next prev parent reply other threads:[~2013-09-19 6:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-18 21:10 [PATCH 1/2] iio: Pass scan mask as unsigned long Peter Meerwald
2013-09-18 21:10 ` [PATCH 2/2] iio: Fix crash when scan_bytes is computed with active_scan_mask == NULL Peter Meerwald
2013-09-19 6:48 ` Lars-Peter Clausen [this message]
2013-09-21 11:32 ` Jonathan Cameron
2013-09-21 11:22 ` [PATCH 1/2] iio: Pass scan mask as unsigned long Jonathan Cameron
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