bpf: verifier: Refactor helper access type tracking

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Previously, the verifier was treating all PTR_TO_STACK registers passed
to a helper call as potentially written to by the helper. However, all
calls to check_stack_range_initialized() already have precise access type
information available.

Rather than treat ACCESS_HELPER as a proxy for BPF_WRITE, pass
enum bpf_access_type to check_stack_range_initialized() to more
precisely track helper arguments.

One benefit from this precision is that registers tracked as valid
spills and passed as a read-only helper argument remain tracked after
the call.  Rather than being marked STACK_MISC afterwards.

An additional benefit is the verifier logs are also more precise. For
this particular error, users will enjoy a slightly clearer message. See
included selftest updates for examples.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/ff885c0e5859e0cd12077c3148ff0754cad4f7ed.1736886479.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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This commit is contained in:

Daniel Xu 2025-01-14 13:28:44 -07:00 • committed by Alexei Starovoitov

parent 8ac412a336

commit 37cce22dbd

13 changed files with 42 additions and 54 deletions

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45

kernel/bpf/verifier.c

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tools/testing/selftests/bpf/progs/dynptr_fail.c

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tools/testing/selftests/bpf/progs/test_global_func10.c

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tools/testing/selftests/bpf/progs/uninit_stack.c

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tools/testing/selftests/bpf/progs/verifier_basic_stack.c

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tools/testing/selftests/bpf/progs/verifier_const_or.c

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tools/testing/selftests/bpf/progs/verifier_helper_access_var_len.c

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tools/testing/selftests/bpf/progs/verifier_int_ptr.c

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tools/testing/selftests/bpf/progs/verifier_mtu.c

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tools/testing/selftests/bpf/progs/verifier_raw_stack.c

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tools/testing/selftests/bpf/progs/verifier_unpriv.c

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tools/testing/selftests/bpf/progs/verifier_var_off.c

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tools/testing/selftests/bpf/verifier/calls.c

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