qmemman: fix units on meminfo parsing

meminfo (written by VM) is expected report KiB, but qmemman internally
use bytes. Convert units.
And also move obscure unit conversion in is_meminfo_suspicious to more
logical place in sanitize_and_parse_meminfo.

qubes/qmemman/algo.py

@@ -42,10 +42,11 @@ def sanitize_and_parse_meminfo(untrusted_meminfo):
     # new syntax - just one int
     try:
         if int(untrusted_meminfo) >= 0:
-            return int(untrusted_meminfo)
+            return int(untrusted_meminfo) * 1024
     except ValueError:
         pass
 
+    untrusted_meminfo = untrusted_meminfo.decode('ascii', errors='strict')
     # not new syntax - try the old one
     untrusted_dict = {}
     # split meminfo contents into lines
@@ -61,9 +62,9 @@ def sanitize_and_parse_meminfo(untrusted_meminfo):
     if not is_meminfo_suspicious(untrusted_dict):
         # sanitize end
         meminfo = untrusted_dict
-        return meminfo['MemTotal'] - \
-            meminfo['MemFree'] - meminfo['Cached'] - meminfo['Buffers'] + \
-            meminfo['SwapTotal'] - meminfo['SwapFree']
+        return (meminfo['MemTotal'] -
+            meminfo['MemFree'] - meminfo['Cached'] - meminfo['Buffers'] +
+            meminfo['SwapTotal'] - meminfo['SwapFree']) * 1024
 
 
     return None
@@ -78,7 +79,7 @@ def is_meminfo_suspicious(untrusted_meminfo):
     try:
         for i in ('MemTotal', 'MemFree', 'Buffers', 'Cached',
                 'SwapTotal', 'SwapFree'):
-            val = int(untrusted_meminfo[i])*1024
+            val = int(untrusted_meminfo[i])
             if val < 0:
                 ret = True
             untrusted_meminfo[i] = val

qubes/tools/qmemmand.py

@@ -137,7 +137,7 @@ def meminfo_changed(self, domain_id):
         self.log.debug('meminfo_changed(domain_id={!r})'.format(domain_id))
         untrusted_meminfo_key = self.handle.read(
             '', get_domain_meminfo_key(domain_id))
-        if untrusted_meminfo_key == None or untrusted_meminfo_key == '':
+        if untrusted_meminfo_key == None or untrusted_meminfo_key == b'':
             return
 
         self.log.debug('acquiring global_lock')