From 22ec1a2aea73b9dfe340dff7945bd85af4cc6280 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 1 Dec 2017 13:19:39 -0800 Subject: /dev/mem: Add bounce buffer for copy-out As done for /proc/kcore in commit df04abfd181a ("fs/proc/kcore.c: Add bounce buffer for ktext data") this adds a bounce buffer when reading memory via /dev/mem. This is needed to allow kernel text memory to be read out when built with CONFIG_HARDENED_USERCOPY (which refuses to read out kernel text) and without CONFIG_STRICT_DEVMEM (which would have refused to read any RAM contents at all). Since this build configuration isn't common (most systems with CONFIG_HARDENED_USERCOPY also have CONFIG_STRICT_DEVMEM), this also tries to inform Kconfig about the recommended settings. This patch is modified from Brad Spengler/PaX Team's changes to /dev/mem code in the last public patch of grsecurity/PaX based on my understanding of the code. Changes or omissions from the original code are mine and don't reflect the original grsecurity/PaX code. Reported-by: Michael Holzheu Fixes: f5509cc18daa ("mm: Hardened usercopy") Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- security/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'security') diff --git a/security/Kconfig b/security/Kconfig index e8e449444e65..3b4effd8bbc2 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -143,6 +143,7 @@ config HARDENED_USERCOPY bool "Harden memory copies between kernel and userspace" depends on HAVE_HARDENED_USERCOPY_ALLOCATOR select BUG + imply STRICT_DEVMEM help This option checks for obviously wrong memory regions when copying memory to/from the kernel (via copy_to_user() and -- cgit v1.2.3-59-g8ed1b