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

[Marcos Paulo de Souza]

On Mon, 2026-05-25 at 00:24 +0000, sashiko-bot@xxxxxxxxxx wrote:
> 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.
> --
> 
> commit 532c1b8c7438f534fd4e3440716ede6cf83efe1c
> Author: Marcos Paulo de Souza <mpdesouza@xxxxxxxx>
> 
> 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_targe
> > t.c
> > b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_targe
> > t.c
> > index 9643984d24022..1382a266825fb 100644
> > ---
> > a/tools/testing/selftests/livepatch/test_modules/test_klp_mod_targe
> > t.c
> > +++
> > b/tools/testing/selftests/livepatch/test_modules/test_klp_mod_targe
> > t.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?

Indeed! I'll send a v2 addressing the missing argument. Thanks Sachiko
for spotting it :)