pari: fix off-by-one error

Done by applying upstream patch. Will be included in the next release.

Upstream: https://pari.math.u-bordeaux.fr/cgi-bin/bugreport.cgi?bug=2117

pkgs/applications/science/math/pari/default.nix

@@ -1,5 +1,6 @@
 { stdenv
 , fetchurl
+, fetchpatch
 , gmp
 , readline
 , libX11
@@ -19,6 +20,18 @@ stdenv.mkDerivation rec {
     sha256 = "1jfax92jpydjd02fwl30r6b8kfzqqd6sm4yx94gidyz9lqjb7a94";
   };
 
+  patches = [
+    # Fix a off-by-one bug that can potentially lead to segfaults (accepted upstream)
+    # https://pari.math.u-bordeaux.fr/cgi-bin/bugreport.cgi?bug=2117
+    # https://trac.sagemath.org/ticket/27335
+    (fetchpatch {
+      name = "fix-off-by-one-error.patch";
+      # only relevant parts of https://pari.math.u-bordeaux.fr/cgi-bin/gitweb.cgi?p=pari.git;a=patch;h=aa1ee6e0898d177e6bcf49237d82c804bc410985
+      url = "https://git.sagemath.org/sage.git/plain/build/pkgs/pari/patches/red_montgomery.patch?id=bbea55c96e1f05302b3c7f593cf64492497047c5";
+      sha256 = "0vqkmhgv9splsdswp6zjnkj50z76rc1m6k9iy3cf9dxwqw3h3nr6";
+    })
+  ];
+
   buildInputs = [
     gmp
     readline