Re: [PATCH v7 4/4] kallsyms: add KUnit tests for lineinfo feature

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Unchecked NULL pointer dereference when allocating test symbol buffer.
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--- Patch [4]: [PATCH v7 4/4] kallsyms: add KUnit tests for lineinfo feature ---
commit aa7a75a3dcd2a5f7456eb96f884496c36509f6d7
Author: Sasha Levin <sashal@kernel.org>

    kallsyms: add KUnit tests for lineinfo feature

This commit adds a KUnit test module to verify that the kallsyms lineinfo
feature produces correct annotations in stack traces. It also exports
sprint_backtrace() and sprint_backtrace_build_id() so the test module can
exercise the backtrace APIs.

> diff --git a/lib/tests/lineinfo_kunit.c b/lib/tests/lineinfo_kunit.c
> new file mode 100644
> index 0000000000000..dad1522a44f5a
> --- /dev/null
> +++ b/lib/tests/lineinfo_kunit.c
[ ... ]
> +static char *alloc_sym_buf(struct kunit *test)
> +{
> +	return kunit_kzalloc(test, KSYM_SYMBOL_LEN, GFP_KERNEL);
> +}
[ ... ]
> +static void test_normal_function(struct kunit *test)
> +{
> +	char *buf = alloc_sym_buf(test);
> +	unsigned long addr = target_addr(lineinfo_target_normal);
> +
> +	skip_without_module_lineinfo(test);
> +
> +	sprint_with_lineinfo(buf, addr);

[Severity: Medium]
Will this crash the kernel if kunit_kzalloc() fails and returns NULL?

If memory allocation fails under pressure, alloc_sym_buf() returns NULL. The
callers like test_normal_function() pass this buffer unchecked into
sprint_with_lineinfo(), which eventually passes it to kallsyms_lookup_buildid()
as the namebuf parameter.

Looking at kallsyms_lookup_buildid() in kernel/kallsyms.c, the buffer is
dereferenced immediately:

kernel/kallsyms.c:kallsyms_lookup_buildid() {
    ...
    namebuf[0] = 0;
    ...
}

Should alloc_sym_buf() use KUNIT_ASSERT_NOT_NULL(test, buf) to gracefully fail
the test instead of causing a NULL pointer dereference?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709163833.3851179-1-sashal@kernel.org?part=4