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

[David Holmes]

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.

To get to the point where we crash this way a lot of stuff under lib has to exist and be readable (e.g. native libs), so why is modules not readable?

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PR Comment: https://git.openjdk.org/jdk/pull/28982#issuecomment-3708991647