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Today if `libffi` cannot allocate pages of memory which are both writeable and executable then it will attempt to write code to a temporary file. Elasticsearch configures itself a suitable temporary directory for use by JNA but by default `libffi` won't find this directory and will try various other places. In certain configurations, none of the other places that `libffi` tries are suitable. With older versions of JNA this would result in a `SIGSEGV`; since #80617 the JVM will exit with an exception. With this commit we use the `LIBFFI_TMPDIR` environment variable to configure `libffi` to use the same directory as JNA for its temporary files if they are needed. Closes #18272 Closes #73309 Closes #74545 Closes #77014 Closes #77053 Relates #77285 Co-authored-by: Rory Hunter <roryhunter2@gmail.com>
37 lines
1.8 KiB
Text
37 lines
1.8 KiB
Text
[[executable-jna-tmpdir]]
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=== JNA temporary directory not mounted with `noexec`
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[NOTE]
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This is only relevant for Linux.
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{es} uses the Java Native Access (JNA) library, and another library called
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`libffi`, for executing some platform-dependent native code. On Linux, the
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native code backing these libraries is extracted at runtime into a temporary
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directory and then mapped into executable pages in {es}'s address space. This
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requires the underlying files not to be on a filesystem mounted with the
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`noexec` option.
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By default, {es} will create its temporary directory within `/tmp`. However,
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some hardened Linux installations mount `/tmp` with the `noexec` option by
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default. This prevents JNA and `libffi` from working correctly. For instance,
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at startup JNA may fail to load with an `java.lang.UnsatisfiedLinkerError`
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exception or with a message that says something similar to
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`failed to map segment from shared object`. Note that the exception message can
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differ amongst JVM versions. Additionally, the components of {es} that rely on
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execution of native code via JNA may fail with messages indicating that it is
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`because JNA is not available`.
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To resolve these problems, either remove the `noexec` option from your `/tmp`
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filesystem, or configure {es} to use a different location for its temporary
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directory by setting the <<es-tmpdir,`$ES_TMPDIR`>> environment variable. For
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instance:
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["source","sh",subs="attributes"]
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--------------------------------------------
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export ES_TMPDIR=/usr/share/elasticsearch/tmp
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--------------------------------------------
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Alternatively, you can configure the path that JNA uses for its temporary files
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with the <<set-jvm-options,JVM flag>> `-Djna.tmpdir=<path>` and you can
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configure the path that `libffi` uses for its temporary files with the
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`LIBFFI_TMPDIR` environment variable.
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