selftests: vDSO: ensure vgetrandom works in a time namespace

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After verifying that vDSO getrandom does work, which ensures that the
RNG is initialized, test to see if it also works inside of a time
namespace. This is important to test, because the vvar pages get
swizzled around there. If the arch code isn't careful, the RNG will
appear uninitialized inside of a time namespace.

Because broken code makes the RNG appear uninitialized, test that
everything works by issuing a call to vgetrandom from a fork in a time
namespace, and use ptrace to ensure that the actual syscall getrandom
doesn't get called. If it doesn't get called, then the test succeeds.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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Jason A. Donenfeld 2024-09-05 19:17:24 +02:00

parent 33ffa2dd0d

commit 2aec90036d

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tools/testing/selftests/vDSO/vdso_test_getrandom.c

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