iio: Fix a buffer overflow in iio_utils.h example code

This was originally reported by Craig Markwardt on Zubair Lutfullah's
blog and Zubair forwarded it to linux-iio@vger.kernel.org. No email
address known.

The code first counted the number of enabled channels, then created an
array to hold information about them.  The code that filled this array then
stored whether a given element was enabled inside the array.  Curriously
this element was never used.  Craig's patch added a local temporary variable
to avoid the buffer overrun.  Jonathan then removed the original enabled
element of the structure as it was not needed at all.

Signed-off-by: Zubair Lutfullah <zubair.lutfullah@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/Documentation/iio_utils.h b/drivers/staging/iio/Documentation/iio_utils.h
index 35154d60faf6120813bb26bf2477994e66fd259f..c9fedb79e3a2d2cec92f04a7860c6e2c055bd0fc 100644 (file)
--- a/drivers/staging/iio/Documentation/iio_utils.h
+++ b/drivers/staging/iio/Documentation/iio_utils.h
@@ -77,7 +77,6 @@ struct iio_channel_info {
        uint64_t mask;
        unsigned be;
        unsigned is_signed;
-       unsigned enabled;
        unsigned location;
 };
 
@@ -335,6 +334,7 @@ inline int build_channel_array(const char *device_dir,
        while (ent = readdir(dp), ent != NULL) {
                if (strcmp(ent->d_name + strlen(ent->d_name) - strlen("_en"),
                           "_en") == 0) {
+                       int current_enabled = 0;
                        current = &(*ci_array)[count++];
                        ret = asprintf(&filename,
                                       "%s/%s", scan_el_dir, ent->d_name);
@@ -350,10 +350,10 @@ inline int build_channel_array(const char *device_dir,
                                ret = -errno;
                                goto error_cleanup_array;
                        }
-                       fscanf(sysfsfp, "%u", &current->enabled);
+                       fscanf(sysfsfp, "%u", &current_enabled);
                        fclose(sysfsfp);
 
-                       if (!current->enabled) {
+                       if (!current_enabled) {
                                free(filename);
                                count--;
                                continue;