linux.git/tools/testing/selftests/bpf/prog_tests/test_map_uninit.c, branch master Linux kernel source tree selftests/bpf: Verify no non-zeroed kernel heap memory exposure 2026-07-01T18:27:37+00:00 Leon Hwang leon.hwang@linux.dev 2026-06-24T15:51:15+00:00 163944262f8646bf3a1eec557b6aff1f38582a9f 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 
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