Author: kib
Date: Thu Jan 11 12:07:24 2018
New Revision: 327816
URL: https://svnweb.freebsd.org/changeset/base/327816
Log:
Update comment explaining the check, to reality.
Discussed with: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Modified:
head/sys/amd64/amd64/support.S
head/sys/i386/i386/support.s
Modified: head/sys/amd64/amd64/support.S
==============================================================================
--- head/sys/amd64/amd64/support.S Thu Jan 11 09:42:24 2018
(r327815)
+++ head/sys/amd64/amd64/support.S Thu Jan 11 12:07:24 2018
(r327816)
@@ -249,12 +249,10 @@ ENTRY(copyout)
jz done_copyout
/*
- * Check explicitly for non-user addresses. If 486 write protection
- * is being used, this check is essential because we are in kernel
- * mode so the h/w does not provide any protection against writing
- * kernel addresses.
+ * Check explicitly for non-user addresses. This check is essential
+ * because it prevents usermode from writing into kernel. We do not
+ * verify that user did not specified a rogue address anywhere else.
*/
-
/*
* First, prevent address wrapping.
*/
Modified: head/sys/i386/i386/support.s
==============================================================================
--- head/sys/i386/i386/support.s Thu Jan 11 09:42:24 2018
(r327815)
+++ head/sys/i386/i386/support.s Thu Jan 11 12:07:24 2018
(r327816)
@@ -291,12 +291,10 @@ ENTRY(copyout)
jz done_copyout
/*
- * Check explicitly for non-user addresses. If 486 write protection
- * is being used, this check is essential because we are in kernel
- * mode so the h/w does not provide any protection against writing
- * kernel addresses.
+ * Check explicitly for non-user addresses. This check is essential
+ * because it prevents usermode from writing into kernel. We do not
+ * verify that user did not specified a rogue address anywhere else.
*/
-
/*
* First, prevent address wrapping.
*/
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