driver: iio: add missing checks on iio_info's callback access

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@analog.com>
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Link: https://lore.kernel.org/r/20240530-iio-core-fix-segfault-v3-1-8b7cd2a03773@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index fa7cc05..2f185b3 100644 (file)
--- 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 910c1f1..a64f8fb 100644 (file)
--- 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 52d7732..77cf1f2 100644 (file)
--- 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,