From ae531c26c5c2a28ca1b35a75b39b3b256850f2c8 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Thu, 24 Apr 2008 23:40:47 +0200 Subject: x86: introduce /dev/mem restrictions with a config option This patch introduces a restriction on /dev/mem: Only non-memory can be read or written unless the newly introduced config option is set. The X server needs access to /dev/mem for the PCI space, but it doesn't need access to memory; both the file permissions and SELinux permissions of /dev/mem just make X effectively super-super powerful. With the exception of the BIOS area, there's just no valid app that uses /dev/mem on actual memory. Other popular users of /dev/mem are rootkits and the like. (note: mmap access of memory via /dev/mem was already not allowed since a really long time) People who want to use /dev/mem for kernel debugging can enable the config option. The restrictions of this patch have been in the Fedora and RHEL kernels for at least 4 years without any problems. Signed-off-by: Arjan van de Ven Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- include/asm-x86/page.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/asm-x86/page.h b/include/asm-x86/page.h index 6724a4bc6b7a..b381f4a5a0bd 100644 --- a/include/asm-x86/page.h +++ b/include/asm-x86/page.h @@ -47,6 +47,7 @@ #ifndef __ASSEMBLY__ extern int page_is_ram(unsigned long pagenr); +extern int devmem_is_allowed(unsigned long pagenr); extern unsigned long max_pfn_mapped; -- cgit v1.2.3