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2ef3cec44c
As noticed by Brian, KMSAN should not be zeroing the origin when unpoisoning parts of a four-byte uninitialized value, e.g.: char a[4]; kmsan_unpoison_memory(a, 1); This led to false negatives, as certain poisoned values could receive zero origins, preventing those values from being reported. To fix the problem, check that kmsan_internal_set_shadow_origin() writes zero origins only to slots which have zero shadow. Link: https://lkml.kernel.org/r/20240528104807.738758-1-glider@google.com Fixes: f80be4571b19 ("kmsan: add KMSAN runtime core") Signed-off-by: Alexander Potapenko <glider@google.com> Reported-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com> Link: https://lore.kernel.org/lkml/20240524232804.1984355-1-bjohannesmeyer@gmail.com/T/ Reviewed-by: Marco Elver <elver@google.com> Tested-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>