Re: [PATCH v6 3/8] vfio: selftests: Introduce a sysfs lib

[David Matlack <dmatlack@google.com>]

On 2026-03-03 07:38 PM, Raghavendra Rao Ananta wrote:

> +	ret = readlink(path, vf_path, PATH_MAX);
> +	VFIO_ASSERT_NE(ret, -1);
> +	vf_path[ret] = '\0';

...

> +	ret = readlink(path, dev_iommu_group_path, sizeof(dev_iommu_group_path));
> +	VFIO_ASSERT_NE(ret, -1, "Failed to get the IOMMU group for device: %s\n", bdf);
> +	dev_iommu_group_path[ret] = '\0';

...

> +	ret = readlink(path, driver_path, PATH_MAX);
> +	if (ret == -1) {
> +		free(out_driver);
> +
> +		if (errno == ENOENT)
> +			return NULL;
> +
> +		VFIO_FAIL("Failed to read %s\n", path);
> +	}
> +	driver_path[ret] = '\0';

These can all write off the end of the buffer if ret == PATH_MAX.

Also there is an inconsistency in these calls. 2 use hard-coded PATH_MAX
while the other uses sizeof().

Perhaps add a wrapper to handle all the details?

#define readlink_safe(path, buf) ({                           \
	int __ret = readlink(_path, _buf, sizeof(_buf) - 1);  \
	if (__ret != -1)                                      \
		_buf[__ret] = 0;                              \
	__ret;
})