selftests/bpf: Verify no non-zeroed kernel heap memory exposure

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When lookup element from those per-CPU maps, which have special field
in their values and their value size is not equal to roundup(value_sz, 8),
the padding size of temporary non-zeroed kernel heap memory allocated by
kvmalloc should not be exposed to user space.

Without the fix:

test_map_uninit_mem_exposure:FAIL:zeroed tail bytes unexpected memory mismatch
actual:
	2B 2B 2B 2B
expected:
	00 00 00 00

Assisted-by: Codex:gpt-5.5

Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260624155115.85196-3-leon.hwang@linux.dev

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Leon Hwang 2026-06-24 23:51:15 +08:00 • committed by Andrii Nakryiko

parent 7cf9cd98cf

commit 163944262f

2 changed files with 80 additions and 0 deletions

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68

tools/testing/selftests/bpf/prog_tests/test_map_uninit.c

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12

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

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