Don't chmod symlink before moving outputs around

Co-authored-by: Théophane Hufschmitt <regnat@users.noreply.github.com>

2 files changed, 11 insertions, 3 deletions

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index ba28e78c8..f406c89d2 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -2065,7 +2065,7 @@ void linkOrCopy(const Path & from, const Path & to)
            file (e.g. 32000 of ext3), which is quite possible after a
            'nix-store --optimise'. FIXME: actually, why don't we just
            bind-mount in this case?
-           
+
            It can also fail with EPERM in BeegFS v7 and earlier versions
            which don't allow hard-links to other directories */
         if (errno != EMLINK && errno != EPERM)
@@ -4101,8 +4101,13 @@ void DerivationGoal::registerOutputs()
                     if (lstat(actualPath.c_str(), &st))
                         throw SysError("getting attributes of path '%1%'", actualPath);
                     mode |= 0200;
-                    if (chmod(actualPath.c_str(), mode) == -1)
-                        throw SysError("changing mode of '%1%' to %2$o", actualPath, mode);
+                    /* Try to change the perms, but only if the file isn't a
+                       symlink as symlinks permissions are mostly ignored and
+                       calling `chmod` on it will just forward the call to the
+                       target of the link. */
+                    if (!S_ISLNK(st.st_mode))
+                        if (chmod(actualPath.c_str(), mode) == -1)
+                            throw SysError("changing mode of '%1%' to %2$o", actualPath, mode);
                 }
                 if (rename(
                         actualPath.c_str(),
diff --git a/tests/content-addressed.nix b/tests/content-addressed.nix
index b0eb29c3f..5e9bad0ac 100644
--- a/tests/content-addressed.nix
+++ b/tests/content-addressed.nix
@@ -16,11 +16,14 @@ rec {
   };
   rootCA = mkDerivation {
     name = "dependent";
+    outputs = [ "out" "dev" ];
     buildCommand = ''
       echo "building a CA derivation"
       echo "The seed is ${toString seed}"
       mkdir -p $out
       echo ${rootLegacy}/hello > $out/dep
+      # test symlink at root
+      ln -s $out $dev
     '';
     __contentAddressed = true;
     outputHashMode = "recursive";