RFR: 8374343: Fix SIGSEGV when lib/modules is unreadable

[Boris Ulasevich]

On Wed, 24 Dec 2025 16:06:30 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

> The JVM crashes with a SIGSEGV during startup if the runtime image (lib/modules) exists but is unreadable. In this scenario, ClassLoader::get_jrt_entry() returns nullptr, leading to a crash. This change adds a null check to avoid the dereference and bail out gracefully.

Right. The asymmetric permission model can occur in hardened, policy-driven customer deployments, where native libraries and runtime images end up being subject to different access rules. We don’t have full details of the original customer setup; however, we can reproduce the same crash by denying access to lib/modules, and we think it’s worth fixing.

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PR Comment: https://git.openjdk.org/jdk/pull/28982#issuecomment-3714845621