Search for patch for kernel stack disclosure in binfmt_script during execve

[halfdog <me@halfdog.net>]

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I'm searching for a patch for linux kernel stack disclosure in
binfmt_script with crafted interpreter names when CONFIG_MODULES is
active (see [1]).

The simplest solution would be to return an error in load_script (from
fs/binfmt_script.c). when maximal recursion depth is reached, but I'm
not sure, if that is nice and could have any side effects. Apart from
that, some change in the loop condition in search_binary_handler (from
fs/exec.c) could have side effects hard to see and hence reintroduce
the bug (challenge to get that right in documentation).


Any comments?

- --- fs/binfmt_script.c  2012-01-19 23:04:48.000000000 +0000
+++ fs/binfmt_script.c        2012-08-18 13:55:25.735748407 +0000
@@ -22,9 +22,8 @@
        char interp[BINPRM_BUF_SIZE];
        int retval;

- -       if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!') ||
- -           (bprm->recursion_depth > BINPRM_MAX_RECURSION))
- -               return -ENOEXEC;
+       if ((bprm->buf[0] != '#') || (bprm->buf[1] != '!')) return
- -ENOEXEC;
+        if (bprm->recursion_depth > BINPRM_MAX_RECURSION) return -ENOMEM;
        /*
         * This section does the #! interpretation.
         * Sorta complicated, but hopefully it will work.  -TYT

hd

[1]
http://www.halfdog.net/Security/2012/LinuxKernelBinfmtScriptStackDataDisclosure/

- -- 
http://www.halfdog.net/
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