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spring-framework/spring-core
Sam Brannen 15ef2b21f0 Handle synchronous exceptions from AsynchronousFileChannel#read
Prior to this commit, DataBufferUtils$ReadCompletionHandler#read()
invoked AsynchronousFileChannel#read(ByteBuffer, long, Attachment,
CompletionHandler) without guarding against exceptions thrown directly
by that call. Although that method is documented to report failures
asynchronously via the supplied CompletionHandler, some platform-
specific implementations can instead throw synchronously – for
example, on Windows with JDK 25, when the JDK rejects a ByteBuffer
backed by a closeable shared memory Arena, as produced by Netty 4.2's
off-heap buffer allocation.

When such an exception is thrown from a recursive read() invocation
triggered from completed() – which happens once a resource requires
more than a single chunk – the exception has no path back to the
FluxSink: it escapes on whatever thread invoked the CompletionHandler,
and the resulting Flux never signals onError or onComplete. In
practice, this surfaced as an indefinite hang when serving a Resource
whose HTTP response is not a ZeroCopyHttpOutputMessage, since
ResourceHttpMessageWriter falls back to ResourceEncoder, which reads
the resource via DataBufferUtils.

To address that, this commit wraps the channel.read(...) call in a
try/catch block and routes any non-fatal Throwable to the existing
failed(Throwable, Attachment) handler, via Exceptions.throwIfFatal(),
mirroring the equivalent fix already applied to the write side for
gh-36184. This ensures the allocated DataBuffer is released and the
Flux always terminates with a proper error signal instead of leaking a
buffer or hanging silently.

See gh-36184
Closes gh-37143
2026-08-18 16:32:34 +02:00
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