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[Deepin-Kernel-SIG] [linux 6.6-y] bpf: a temporary fix for bpf_lsm_mmap_file null access #1435

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opsiff merged 1 commit into from
Jan 15, 2026
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[Deepin-Kernel-SIG] [linux 6.6-y] bpf: a temporary fix for bpf_lsm_mmap_file null access #1435

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7 changes: 7 additions & 0 deletions kernel/bpf/btf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6092,6 +6092,13 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
if (prog_arg_maybe_null(prog, btf, &args[arg]))
info->reg_type |= PTR_MAYBE_NULL;

/* a temporary workaround for bpf_lsm_mmap_file null pointer access,
* ugly but effective, should be removed while BTF weak symbol is
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Copilot AI Jan 14, 2026

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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".

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

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* supported by pahole
*/
if (!strcmp(tname, "bpf_lsm_mmap_file") && arg == 0)
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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.

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info->reg_type |= PTR_MAYBE_NULL;

if (tgt_prog) {
enum bpf_prog_type tgt_type;

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