[Deepin-Kernel-SIG] [linux 6.12-y] bpf: a temporary supplement 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:
patch1: #1392
patch2: #1393

Summary by Sourcery

Bug Fixes:

• Prevent potential null pointer access when handling the first parameter of the bpf_lsm_mmap_file hook by treating it as maybe-null in BPF verifier context.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Temporarily relaxes BTF-based nullability checking for the first argument of the bpf_lsm_mmap_file hook by forcing its context pointer to be treated as maybe-null during BPF verification, working around missing BTF weak symbol override support in pahole.

File-Level Changes

Change	Details	Files
Force the first argument of bpf_lsm_mmap_file to be treated as a maybe-null pointer as a temporary workaround for potential null access.	Extend btf_ctx_access to unconditionally mark the first parameter of bpf_lsm_mmap_file as PTR_MAYBE_NULL in verifier metadata Guard the workaround with a specific function-name check using strcmp and argument index 0 Document in comments that this is a temporary workaround to be removed once pahole supports BTF weak symbol overrides	kernel/bpf/btf.c

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[deepin-ci-robot]

Hi @lax-fly. Thanks for your PR.

I'm waiting for a deepin-community member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: opsiff

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[Copilot]

Pull request overview

This PR adds a temporary workaround to prevent null pointer access when handling the first parameter of the bpf_lsm_mmap_file hook in the BPF verifier. The fix manually marks this parameter as potentially null until pahole gains support for BTF weak symbol override, at which point this workaround should be removed.

Key Changes:

• Added explicit null-safety check for bpf_lsm_mmap_file's first parameter in BPF context access validation

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[Copilot]

Spelling error in comment: "urgly" should be "ugly".

Suggested change

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