[ostree] prepare-root: Fix ostree= kernel argument at end

[Colin Walters <walters src gnome org>]

commit 9e497a4ce7cfde5db9605353590c1fe037f969ac
Author: Colin Walters <walters verbum org>
Date:   Sun Sep 1 04:16:52 2013 -0400

    prepare-root: Fix ostree= kernel argument at end
    
    Extracting the code for parse_ostree_cmdline() and running it on some
    test input (on RHEL6.4 glibc), I can reproduce the odd behavior from
    getline() where it apparently returns the size of the default malloc
    buffer in the size output, and some non-zero value.
    
    This behavior would be OK except that it breaks the logic for
    stripping off the trailing newline, which in turn breaks booting
    because we return "ostree=foo\n".
    
    This has worked so far in gnome-ostree because syslinux apparently
    injects initrd=/path/to/initrd as a final kernel argment.
    
    Anyways, we don't handle NUL characters here in /proc/cmdline, so
    let's just call strlen () to be safe.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707192

 src/switchroot/ostree-prepare-root.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/src/switchroot/ostree-prepare-root.c b/src/switchroot/ostree-prepare-root.c
index a77da7c..25ac66b 100644
--- a/src/switchroot/ostree-prepare-root.c
+++ b/src/switchroot/ostree-prepare-root.c
@@ -54,8 +54,15 @@ parse_ostree_cmdline (void)
 
   if (!f)
     return NULL;
+  /* Note that /proc/cmdline will not end in a newline, so getline
+   * will fail unelss we provide a length.
+   */
   if (getline (&cmdline, &len, f) < 0)
     return NULL;
+  /* ... but the length will be the size of the malloc buffer, not
+   * strlen().  Fix that.
+   */
+  len = strlen (cmdline);
 
   if (cmdline[len-1] == '\n')
     cmdline[len-1] = '\0';