Re: [PATCH 3/4] selftests: livepatch: Adapt mod_target module to pass on 4.12 kernels

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `test_klp_mod_target_ops` structure omits the logically required `.set` callback, exposing the kernel to a NULL pointer dereference during module load.
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commit 532c1b8c7438f534fd4e3440716ede6cf83efe1c
Author: Marcos Paulo de Souza <[email protected]>

selftests: livepatch: Adapt mod_target module to pass on 4.12 kernels

Use the stable module_param_cb API instead of proc_fs for exposing module
state. This approach is compatible with kernel 4.12 and later.

> diff --git a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
> index 9643984d24022..1382a266825fb 100644
> --- a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
> +++ b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_target.c
> @@ -5,31 +5,29 @@
[ ... ]
> +static const struct kernel_param_ops test_klp_mod_target_ops = {
> +	.get = test_klp_mod_target_get,
> +};
> +
> +module_param_cb(klp_mod_arg, &test_klp_mod_target_ops, NULL, 0444);

[Severity: Medium]
Does this code need a .set callback in the kernel_param_ops structure?

When a module parameter is passed during module load, the kernel parses the
arguments using parse_args(), which invokes parse_one() in kernel/params.c.
Because parse_one() unconditionally executes the .set callback without
verifying if it is actually defined, omitting it here leaves the callback
implicitly initialized to NULL.

Could this lead to a NULL pointer dereference and a kernel panic if someone
attempts to set this parameter during module load?

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Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=3