gpio-sim: fix memory corruption when adding named lines and unnamed hogs

When constructing the sim, gpio-sim constructs an array of named lines, sized based on the largest offset of any named line, and then initializes that array with the names of all lines, including unnamed hogs with higher offsets. In doing so it writes NULLs beyond the extent of the array.

Add a check that only named lines are used to initialize the array.

Fixes cb8c474e79be ("gpio: sim: new testing module")

Signed-off-by Kent Gibson <[email protected]>

---

After writing the comment above, and looking at the code again, it may be clearer to instead check that the offset is within the bounds of the array. Or do both. Consider that my review.

Cheers,
Kent.

 drivers/gpio/gpio-sim.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

drivers/gpio/gpio-sim.c +4 -3

index e5dfd636c63c..923e8ff53128 100644
@@ -721,8 +721,10 @@ static char **gpio_sim_make_line_names(struct gpio_sim_bank *bank,
        if (!line_names)
                return ERR_PTR(-ENOMEM);
 
-       list_for_each_entry(line, &bank->line_list, siblings)
-               line_names[line->offset] = line->name;
+       list_for_each_entry(line, &bank->line_list, siblings) {
+               if (line->name)
+                       line_names[line->offset] = line->name;
+       }
 
        return line_names;
 }
--

2.40.1

Quoted 8 lines · Kent Gibson

When constructing the sim, gpio-sim constructs an array of named lines, sized based on the largest offset of any named line, and then initializes that array with the names of all lines, including unnamed hogs with higher offsets. In doing so it writes NULLs beyond the extent of the array.

Add a check that only named lines are used to initialize the array.

Quoted 8 lines

Fixes cb8c474e79be ("gpio: sim: new testing module")

Signed-off-by Kent Gibson <[email protected]>

---

After writing the comment above, and looking at the code again, it may be clearer to instead check that the offset is within the bounds of the array. Or do both. Consider that my review.

Like:

if (line->offset <= max_offset)

    line_names[line->offset] = line->name;

? If so, then I agree it makes the purpose of the check clearer.

Quoted 18 lines · Bartosz Golaszewski

Quoted 8 lines · Kent Gibson

When constructing the sim, gpio-sim constructs an array of named lines, sized based on the largest offset of any named line, and then initializes that array with the names of all lines, including unnamed hogs with higher offsets. In doing so it writes NULLs beyond the extent of the array.

Add a check that only named lines are used to initialize the array.

Quoted 8 lines

Fixes cb8c474e79be ("gpio: sim: new testing module")

Signed-off-by Kent Gibson <[email protected]>

---

After writing the comment above, and looking at the code again, it may be clearer to instead check that the offset is within the bounds of the array. Or do both. Consider that my review.

Quoted 7 lines

Like:

if (line->offset <= max_offset)

    line_names[line->offset] = line->name;

? If so, then I agree it makes the purpose of the check clearer.

Using line_names_size might be even clearer.

So, either that or

if (line->name && (line->offset <= max_offset))

    line_names[line->offset] = line->name;

to also not repeat the zeroing that the kcalloc() did.

Too many options. Let me know which you prefer.

Cheers,
Kent.