If an integer's type has x bits, shifting the integer left by x or more is undefined behavior. This can happen in the rotate function when attempting to do a rotation of the whole value by 0.

Fixes: 0dd714bfd200 ("KVM: s390: selftest: memop: Add cmpxchg tests") Signed-off-by: Nina Schoetterl-Glausch nsg@linux.ibm.com ---

v1 -> v2: use early return instead of modulus

tools/testing/selftests/kvm/s390x/memop.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/kvm/s390x/memop.c b/tools/testing/selftests/kvm/s390x/memop.c index bb3ca9a5d731..4ec8d0181e8d 100644 --- a/tools/testing/selftests/kvm/s390x/memop.c +++ b/tools/testing/selftests/kvm/s390x/memop.c @@ -489,6 +489,8 @@ static __uint128_t rotate(int size, __uint128_t val, int amount)

amount = (amount + bits) % bits; val = cut_to_size(size, val); + if (!amount) + return val; return (val << (bits - amount)) | (val >> amount); }

base-commit: 305230142ae0637213bf6e04f6d9f10bbcb74af8