13/27: libutil: Limit readLink() error to only overflows.

[Ludovic Courtès]

civodul pushed a commit to branch nix
in repository guix.

commit 0b9c4a8b80b199ce82ca5bd08ed24b8d5d5c71f5
Author: aszlig <address@hidden>
Date:   Fri Jan 2 03:45:47 2015 +0100

    libutil: Limit readLink() error to only overflows.
    
    Let's not just improve the error message itself, but also the behaviour
    to actually work around the ntfs-3g symlink bug. If the readlink() call
    returns a smaller size than the stat() call, this really isn't a problem
    even if the symlink target really has changed between the calls.
    
    So if stat() reports the size for the absolute path, it's most likely
    that the relative path is smaller and thus it should also work for file
    system bugs as mentioned in 93002d69fc58c2b71e2dfad202139230c630c53a.
    
    Signed-off-by: aszlig <address@hidden>
    Tested-by: John Ericson <address@hidden>
---
 nix/libutil/util.cc |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index 410d0f2..dab4235 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -196,8 +196,8 @@ Path readLink(const Path & path)
     ssize_t rlsize = readlink(path.c_str(), buf, st.st_size);
     if (rlsize == -1)
         throw SysError(format("reading symbolic link '%1%'") % path);
-    else if (rlsize != st.st_size)
-        throw Error(format("symbolic link '%1%' size mismatch %2% != %3%")
+    else if (rlsize > st.st_size)
+        throw Error(format("symbolic link ‘%1%’ size overflow %2% > %3%")
             % path % rlsize % st.st_size);
     return string(buf, st.st_size);
 }