File xsa407-0l.patch of Package xen.26348

From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: xen/cmdline: Extend parse_boolean() to signal a name match

This will help parsing a sub-option which has boolean and non-boolean options
available.

First, rework 'int val' into 'bool has_neg_prefix'.  This inverts it's value,
but the resulting logic is far easier to follow.

Second, reject anything of the form 'no-$FOO=' which excludes ambiguous
constructs such as 'no-$foo=yes' which have never been valid.

This just leaves the case where everything is otherwise fine, but parse_bool()
can't interpret the provided string.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit 382326cac528dd1eb0d04efd5c05363c453e29f4)

--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -171,9 +171,9 @@ int __init parse_bool(const char *s)
 int parse_boolean(const char *name, const char *s, const char *e)
 {
     size_t slen, nlen;
-    int val = !!strncmp(s, "no-", 3);
+    bool_t has_neg_prefix = !strncmp(s, "no-", 3);
 
-    if ( !val )
+    if ( has_neg_prefix )
         s += 3;
 
     slen = e ? ({ ASSERT(e >= s); e - s; }) : strlen(s);
@@ -185,7 +185,11 @@ int parse_boolean(const char *name, cons
 
     /* Exact, unadorned name?  Result depends on the 'no-' prefix. */
     if ( slen == nlen )
-        return val;
+        return !has_neg_prefix;
+
+    /* Inexact match with a 'no-' prefix?  Not valid. */
+    if ( has_neg_prefix )
+        return -1;
 
     /* =$SOMETHING?  Defer to the regular boolean parsing. */
     if ( s[nlen] == '=' )
@@ -194,11 +198,20 @@ int parse_boolean(const char *name, cons
 
         s += nlen + 1;
         slen -= nlen + 1;
-        if ( slen >= ARRAY_SIZE(buf) )
-            return -1;
-        memcpy(buf, s, slen);
-        buf[slen] = 0;
-        return parse_bool(buf);
+        if ( slen < ARRAY_SIZE(buf) )
+        {
+            int b;
+
+            memcpy(buf, s, slen);
+            buf[slen] = 0;
+            b = parse_bool(buf);
+
+            if ( b >= 0 )
+                return b;
+        }
+
+        /* Not a boolean, but the name matched.  Signal specially. */
+        return -2;
     }
 
     /* Unrecognised.  Give up. */
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -70,7 +70,8 @@ int parse_bool(const char *s);
 /**
  * Given a specific name, parses a string of the form:
  *   [no-]$NAME[=...]
- * returning 0 or 1 for a recognised boolean, or -1 for an error.
+ * returning 0 or 1 for a recognised boolean.  Returns -1 for general errors,
+ * and -2 for "not a boolean, but $NAME= matches".
  */
 int parse_boolean(const char *name, const char *s, const char *e);