usercopy: remove page-spanning test for now
A custom allocator without __GFP_COMP that copies to userspace has been
found in vmw_execbuf_process[1], so this disables the page-span checker
by placing it behind a CONFIG for future work where such things can be
tracked down later.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1373326
Reported-by: Vinson Lee <vlee@freedesktop.org>
Fixes: f5509cc18daa ("mm: Hardened usercopy")
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/security/Kconfig b/security/Kconfig
index da10d9b..2dfc0ce 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -147,6 +147,17 @@
or are part of the kernel text. This kills entire classes
of heap overflow exploits and similar kernel memory exposures.
+config HARDENED_USERCOPY_PAGESPAN
+ bool "Refuse to copy allocations that span multiple pages"
+ depends on HARDENED_USERCOPY
+ depends on !COMPILE_TEST
+ help
+ When a multi-page allocation is done without __GFP_COMP,
+ hardened usercopy will reject attempts to copy it. There are,
+ however, several cases of this in the kernel that have not all
+ been removed. This config is intended to be used only while
+ trying to find such users.
+
source security/selinux/Kconfig
source security/smack/Kconfig
source security/tomoyo/Kconfig