gpio-hammer: Avoid potential overflow in main

If '-o' was used more than 64 times in a single invocation of gpio-hammer, this could lead to an overflow of the 'lines' array. This commit fixes this by avoiding the overflow and giving a proper diagnostic back to the user

Signed-off-by Gabriel Ravier <[email protected]>

---
 tools/gpio/gpio-hammer.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

tools/gpio/gpio-hammer.c +16 -2

index 0e0060a6e..083399d27 100644
@@ -135,7 +135,14 @@ int main(int argc, char **argv)
                        device_name = optarg;
                        break;
                case 'o':
-                       lines[i] = strtoul(optarg, NULL, 10);
+                       /*
+                        * Avoid overflow. Do not immediately error, we want to
+                        * be able to accurately report on the amount of times
+                        * '-o' was given to give an accurate error message
+                        */
+                       if (i < GPIOHANDLES_MAX)
+                               lines[i] = strtoul(optarg, NULL, 10);
+
                        i++;
                        break;
                case '?':

@@ -143,6 +150,14 @@ int main(int argc, char **argv)
                        return -1;
                }
        }
+
+       if (i >= GPIOHANDLES_MAX) {
+               fprintf(stderr,
+                       "Only %d occurences of '-o' are allowed, %d were found\n",
+                       GPIOHANDLES_MAX, i + 1);
+               return -1;
+       }
+
        nlines = i;
 
        if (!device_name || !nlines) {
--

2.24.1