Mark H Weaver <m...@netris.org> skribis:
> l...@gnu.org (Ludovic Courtès) writes:
>> We could use a self symlink, or we could use something like
>> Mark, WDYT?
>> What remains to be seen is how many packages are affected by this issue,
>> and whether a generic solution needs to be found.
> Unfortunately, it is too widespread. As I just pointed out in
> Among the many packages that include these obfuscated store references,
> one is 'glibc-final'. My attempt to graft 'bash' in 'master' to fix
> CVE-2016-0634 and CVE-2016-7543 has resulted in a system where I cannot
> build *any* derivation, because 'guile-final' crashes during boot while
> its 'glibc-final' tries to find its 'gconv' modules in the ungrafted
> 'glibc-final', which is not available in the build environment.
Out of curiosity, Guile crashes while loading iconv modules, right?
This is surprising because the guile-for-build is always the ungrafted
‘guile-final’ (see ‘gnu-build’ in (guix build-system gnu)).
> So, if our approach is to use -fno-builtin-strcpy, then we will have to
> apply it system-wide, and rebuild all of 'core-updates' from scratch.
Another approach would be to patch GCC, specifically ‘expand_movstr’ in
gcc/builtins.c, which is the part responsible for this optimization,
along these lines (untested):
--- gcc-5.3.0/gcc/builtins.c.orig 2016-10-18 10:45:35.042826368 +0200
+++ gcc-5.3.0/gcc/builtins.c 2016-10-18 10:50:46.080616285 +0200
@@ -3470,6 +3470,19 @@ expand_builtin_mempcpy_args (tree dest,
# define CODE_FOR_movstr CODE_FOR_nothing
+/* Return true if STR is a string denoting a "/gnu/store" file name. */
+store_reference_p (tree str)
+ const char *store;
+ store = getenv ("NIX_STORE") ?: "/gnu/store";
+ return (TREE_STRING_LENGTH (str) > strlen (store)
+ && strncmp (TREE_STRING_POINTER (str), store, strlen (store)));
/* Expand into a movstr instruction, if one is available. Return NULL_RTX if
we failed, the caller should emit a normal call, otherwise try to
get the result in TARGET, if convenient. If ENDP is 0 return the
@@ -3484,7 +3497,9 @@ expand_movstr (tree dest, tree src, rtx
- if (!HAVE_movstr)
+ /* When SRC denotes a store item, do not perform any optimization. See
+ <http://bugs.gnu.org/24703> for background. */
+ if (!HAVE_movstr || store_reference_p (src))
dest_mem = get_memory_rtx (dest, NULL);
In the meantime, we need a workaround. The only option I can think of
is to retain a reference to the ungrafted item by adding a symlink to
diff --git a/guix/grafts.scm b/guix/grafts.scm
index 80ae27e..4de19ae 100644
@@ -127,7 +127,14 @@ recursively applied to dependencies of DRV."
(((names . files) ...)
+ (for-each (match-lambda
+ ((name . file)
+ (symlink file
+ (string-append (assoc-ref %outputs name)
(cut cons "x" <>))
> I've been investigating another approach: to enhance our scanner and
> grafter to handle these 8-byte-chunked references. I believe it is
> feasible, but only if we abandon the ability to change the file names of
> grafts outside of the hash. The reason is that the hash portion of
> store references are surrounded by enough other known characters on both
> sides that the hash portion is almost always contained entirely within
> 8-byte chunks.
I think that would add complexity, would make grafting slower, and
abandoning the ability to change file names would be a regression.
So I’m more in favor of a GCC patch like above, or another compilation