Author: kevans
Date: Thu Sep 12 13:51:43 2019
New Revision: 352244
URL: https://svnweb.freebsd.org/changeset/base/352244
Log:
kenv: assert that an empty static buffer passed in is "empty"
Garbage in the passed-in buffer can cause problems if any attempts to read
the kenv are inadvertently made between init_static_kenv and the first
kern_setenv -- assuming there is one.
This is cheap and easy, so do it. This also helps rule out some class of
bugs as one tries to debug; tunables fetch from the static environment up
until SI_SUB_KMEM + 1, and many of these buffers are global ~4k buffers that
rely on BSS clearing while others just grab a page of free memory and use it
(e.g. xen).
Modified:
head/sys/kern/kern_environment.c
Modified: head/sys/kern/kern_environment.c
==============================================================================
--- head/sys/kern/kern_environment.c Thu Sep 12 12:33:09 2019
(r352243)
+++ head/sys/kern/kern_environment.c Thu Sep 12 13:51:43 2019
(r352244)
@@ -250,6 +250,8 @@ init_static_kenv(char *buf, size_t len)
char *eval;
KASSERT(!dynamic_kenv, ("kenv: dynamic_kenv already initialized"));
+ KASSERT(len == 0 || *buf == '\0',
+ ("kenv: sized buffer must be initially empty"));
/*
* We may be called twice, with the second call needed to relocate
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