[Deepin-Kernel-SIG] [linux 6.6-y] bpf: a temporary fix for bpf_lsm_mmap_file null access

[lax-fly]

fix patch before(check url below for details) might not work until pahole support BTF weak symbol override.
This commit is a temporary workaround, ugly but effective, and should be remove in the future when pahole is updated

fix patch before:
#1393

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[Copilot]

Pull request overview

This pull request adds a temporary workaround for a null pointer access issue in bpf_lsm_mmap_file. The workaround manually marks the first argument as potentially null until pahole tooling gains support for BTF weak symbol override, at which point the existing __nullable suffix mechanism in bpf_lsm_proto.c will work properly.

Changes:

• Added a hardcoded string comparison check in btf_ctx_access() to mark the first argument of bpf_lsm_mmap_file as PTR_MAYBE_NULL

---

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[Copilot]

Using hardcoded string comparison for a single function creates a brittle workaround that doesn't scale. If other LSM hooks have similar null pointer issues, each would require adding another hardcoded function name check. Consider a more systematic approach such as maintaining a list or set of affected functions, or better yet, investigating why the existing __nullable suffix mechanism doesn't work and fixing the root cause.

[Copilot]

Corrected spelling of 'while' to 'when' in the context of future action. The phrase should read "should be removed when BTF weak symbol is supported" rather than "should be removed while BTF weak symbol is supported".

Suggested change

	* ugly but effective, should be removed while BTF weak symbol is
	* ugly but effective, should be removed when BTF weak symbol is

[deepin-ci-robot]

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