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Fix segfault or stack overflow caused by large derivation fields

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This removes a dynamic stack allocation, making the derivation
unparsing logic robust against overflows when large strings are
added to a derivation.
Overflow behavior depends on the platform and stack configuration.

For instance, x86_64-linux/glibc behaves as (somewhat) expected:

$ (ulimit -s 20000; nix-instantiate tests/lang/eval-okay-big-derivation-attr.nix)
error: stack overflow (possible infinite recursion)

$ (ulimit -s 40000; nix-instantiate tests/lang/eval-okay-big-derivation-attr.nix)
error: expression does not evaluate to a derivation (or a set or list of those)

However, on aarch64-darwin:

$ nix-instantiate big-attr.nix                                                                                                                                                                                                                                                       ~
zsh: segmentation fault  nix-instantiate big-attr.nix

This indicates a slight flaw in the single stack protection page
approach that is not encountered with normal stack frames.
This commit is contained in:
Robert Hensing 2022-01-06 01:20:12 +01:00
parent bc443511eb
commit d038a67bd3
3 changed files with 28 additions and 1 deletions
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6
tests/simple.sh
View file

@ -25,3 +25,9 @@ if test "$outPath" != "/foo/lfy1s6ca46rm5r6w4gg9hc0axiakjcnm-dependencies.drv";
echo "hashDerivationModulo appears broken, got $outPath"
exit 1
fi
outPath="$(NIX_REMOTE=local?store=/foo\&real=$TEST_ROOT/real-store nix-instantiate --readonly-mode big-derivation-attr.nix)"
if test "$outPath" != "/foo/xxiwa5zlaajv6xdjynf9yym9g319d6mn-big-derivation-attr.drv"; then
echo "big-derivation-attr.nix hash appears broken, got $outPath. Memory corruption in large drv attr?"
exit 1
fi