On 2022-02-22 14:06, Krzysztof Kozlowski wrote:
On 22/02/2022 14:51, Rasmus Villemoes wrote:
On 22/02/2022 14.27, Krzysztof Kozlowski wrote:
Hi,
Drivers still seem to use driver_override incorrectly. Perhaps my old patch makes sense now? https://lore.kernel.org/all/1550484960-2392-3-git-send-email-krzk@kernel.org...
Not tested - please review and test (e.g. by writing to dirver_override sysfs entry with KASAN enabled).
Perhaps it would make sense to update the core code to release using kfree_const(), allowing drivers to set the initial value with kstrdup_const(). Drivers that currently use kstrdup() or kasprintf() will continue to work [but if they kstrdup() a string literal they could be changed to use kstrdup_const].
The core here means several buses, so the change would not be that small. However I don't see the reason why "driver_override" is special and should be freed with kfree_const() while most of other places don't use it.
The driver_override field definition is here obvious: "char *", so any assignments of "const char *" are logically wrong (although GCC does not warn of this literal string const discarding). Adding kfree_const() is hiding the problem - someone did not read the definition of assigned field.
That's not the issue, though, is it? If I take the struct platform_device definition at face value, this should be perfectly valid:
static char foo[] = "foo"; pdev->driver_override = &foo;
And in fact that's effectively how the direct assignment form works anyway - string literals are static arrays of type char (or wchar_t), *not* const char, however trying to modify them is undefined behaviour.
There's a big difference between "non-const" and "kfree()able", and AFAICS there's no obvious clue that the latter is actually a requirement.
Cheers, Robin.