Re: [PATCH v3] driver: iio: add missing checks on iio_info's callback access

From: Jonathan Cameron
Date: Sun Jun 02 2024 - 08:17:57 EST

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On Thu, 30 May 2024 11:22:46 +0200
Julien Stephan <jstephan@xxxxxxxxxxxx> wrote:

> Some callbacks from iio_info structure are accessed without any check, so
> if a driver doesn't implement them trying to access the corresponding
> sysfs entries produce a kernel oops such as:
>
> [ 2203.527791] Unable to handle kernel NULL pointer dereference at virtual address 00000000 when execute
> [...]
> [ 2203.783416] Call trace:
> [ 2203.783429] iio_read_channel_info_avail from dev_attr_show+0x18/0x48
> [ 2203.789807] dev_attr_show from sysfs_kf_seq_show+0x90/0x120
> [ 2203.794181] sysfs_kf_seq_show from seq_read_iter+0xd0/0x4e4
> [ 2203.798555] seq_read_iter from vfs_read+0x238/0x2a0
> [ 2203.802236] vfs_read from ksys_read+0xa4/0xd4
> [ 2203.805385] ksys_read from ret_fast_syscall+0x0/0x54
> [ 2203.809135] Exception stack(0xe0badfa8 to 0xe0badff0)
> [ 2203.812880] dfa0: 00000003 b6f10f80 00000003 b6eab000 00020000 00000000
> [ 2203.819746] dfc0: 00000003 b6f10f80 7ff00000 00000003 00000003 00000000 00020000 00000000
> [ 2203.826619] dfe0: b6e1bc88 bed80958 b6e1bc94 b6e1bcb0
> [ 2203.830363] Code: bad PC value
> [ 2203.832695] ---[ end trace 0000000000000000 ]---
>
> Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>
> Signed-off-by: Julien Stephan <jstephan@xxxxxxxxxxxx>
Dropped v2 and picked this one up. Oops.

Jonathan

> ---
> Changes in v3:
> - Use local variable in inkern.c to reduce long lines
> - Pick up Nuno reviewed-by tag
> - Link to v2: https://lore.kernel.org/r/20240529-iio-core-fix-segfault-v2-1-7b5a5fa6853f@xxxxxxxxxxxx
>
> Changes in v2:
> - crop dmesg log to show only pertinent info and reduce commit message
> - Link to v1: https://lore.kernel.org/r/20240529-iio-core-fix-segfault-v1-1-7ff1ba881d38@xxxxxxxxxxxx
> ---
> drivers/iio/industrialio-core.c | 7 ++++++-
> drivers/iio/industrialio-event.c | 9 +++++++++
> drivers/iio/inkern.c | 32 ++++++++++++++++++++++----------
> 3 files changed, 37 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index fa7cc051b4c4..2f185b386949 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -758,9 +758,11 @@ static ssize_t iio_read_channel_info(struct device *dev,
> INDIO_MAX_RAW_ELEMENTS,
> vals, &val_len,
> this_attr->address);
> - else
> + else if (indio_dev->info->read_raw)
> ret = indio_dev->info->read_raw(indio_dev, this_attr->c,
> &vals[0], &vals[1], this_attr->address);
> + else
> + return -EINVAL;
>
> if (ret < 0)
> return ret;
> @@ -842,6 +844,9 @@ static ssize_t iio_read_channel_info_avail(struct device *dev,
> int length;
> int type;
>
> + if (!indio_dev->info->read_avail)
> + return -EINVAL;
> +
> ret = indio_dev->info->read_avail(indio_dev, this_attr->c,
> &vals, &type, &length,
> this_attr->address);
> diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
> index 910c1f14abd5..a64f8fbac597 100644
> --- a/drivers/iio/industrialio-event.c
> +++ b/drivers/iio/industrialio-event.c
> @@ -285,6 +285,9 @@ static ssize_t iio_ev_state_store(struct device *dev,
> if (ret < 0)
> return ret;
>
> + if (!indio_dev->info->write_event_config)
> + return -EINVAL;
> +
> ret = indio_dev->info->write_event_config(indio_dev,
> this_attr->c, iio_ev_attr_type(this_attr),
> iio_ev_attr_dir(this_attr), val);
> @@ -300,6 +303,9 @@ static ssize_t iio_ev_state_show(struct device *dev,
> struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
> int val;
>
> + if (!indio_dev->info->read_event_config)
> + return -EINVAL;
> +
> val = indio_dev->info->read_event_config(indio_dev,
> this_attr->c, iio_ev_attr_type(this_attr),
> iio_ev_attr_dir(this_attr));
> @@ -318,6 +324,9 @@ static ssize_t iio_ev_value_show(struct device *dev,
> int val, val2, val_arr[2];
> int ret;
>
> + if (!indio_dev->info->read_event_value)
> + return -EINVAL;
> +
> ret = indio_dev->info->read_event_value(indio_dev,
> this_attr->c, iio_ev_attr_type(this_attr),
> iio_ev_attr_dir(this_attr), iio_ev_attr_info(this_attr),
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index 52d773261828..77cf1f22df31 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -543,6 +543,7 @@ EXPORT_SYMBOL_GPL(devm_iio_channel_get_all);
> static int iio_channel_read(struct iio_channel *chan, int *val, int *val2,
> enum iio_chan_info_enum info)
> {
> + const struct iio_info *iio_info = chan->indio_dev->info;
> int unused;
> int vals[INDIO_MAX_RAW_ELEMENTS];
> int ret;
> @@ -554,15 +555,18 @@ static int iio_channel_read(struct iio_channel *chan, int *val, int *val2,
> if (!iio_channel_has_info(chan->channel, info))
> return -EINVAL;
>
> - if (chan->indio_dev->info->read_raw_multi) {
> - ret = chan->indio_dev->info->read_raw_multi(chan->indio_dev,
> - chan->channel, INDIO_MAX_RAW_ELEMENTS,
> - vals, &val_len, info);
> + if (iio_info->read_raw_multi) {
> + ret = iio_info->read_raw_multi(chan->indio_dev,
> + chan->channel,
> + INDIO_MAX_RAW_ELEMENTS,
> + vals, &val_len, info);
> *val = vals[0];
> *val2 = vals[1];
> + } else if (iio_info->read_raw) {
> + ret = iio_info->read_raw(chan->indio_dev,
> + chan->channel, val, val2, info);
> } else {
> - ret = chan->indio_dev->info->read_raw(chan->indio_dev,
> - chan->channel, val, val2, info);
> + return -EINVAL;
> }
>
> return ret;
> @@ -750,11 +754,15 @@ static int iio_channel_read_avail(struct iio_channel *chan,
> const int **vals, int *type, int *length,
> enum iio_chan_info_enum info)
> {
> + const struct iio_info *iio_info = chan->indio_dev->info;
> +
> if (!iio_channel_has_available(chan->channel, info))
> return -EINVAL;
>
> - return chan->indio_dev->info->read_avail(chan->indio_dev, chan->channel,
> - vals, type, length, info);
> + if (iio_info->read_avail)
> + return iio_info->read_avail(chan->indio_dev, chan->channel,
> + vals, type, length, info);
> + return -EINVAL;
> }
>
> int iio_read_avail_channel_attribute(struct iio_channel *chan,
> @@ -917,8 +925,12 @@ EXPORT_SYMBOL_GPL(iio_get_channel_type);
> static int iio_channel_write(struct iio_channel *chan, int val, int val2,
> enum iio_chan_info_enum info)
> {
> - return chan->indio_dev->info->write_raw(chan->indio_dev,
> - chan->channel, val, val2, info);
> + const struct iio_info *iio_info = chan->indio_dev->info;
> +
> + if (iio_info->write_raw)
> + return iio_info->write_raw(chan->indio_dev,
> + chan->channel, val, val2, info);
> + return -EINVAL;
> }
>
> int iio_write_channel_attribute(struct iio_channel *chan, int val, int val2,
>
> ---
> base-commit: 409b6d632f5078f3ae1018b6e43c32f2e12f6736
> change-id: 20240528-iio-core-fix-segfault-aa74be7eee4a
>
> Best regards,

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