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.

My concern is that we cannot test all possible behaviours for all permutations of making some files accessible and others not.  I do not think it makes any sense to have different access rules for files that form part of the same application.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/28982#issuecomment-3716324921