From a4828f81037f491b2cc986595e3a969a6eeb2fb5 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 14 Dec 2017 12:27:31 +0100 Subject: x86/ldt: Prevent LDT inheritance on exec The LDT is inherited across fork() or exec(), but that makes no sense at all because exec() is supposed to start the process clean. The reason why this happens is that init_new_context_ldt() is called from init_new_context() which obviously needs to be called for both fork() and exec(). It would be surprising if anything relies on that behaviour, so it seems to be safe to remove that misfeature. Split the context initialization into two parts. Clear the LDT pointer and initialize the mutex from the general context init and move the LDT duplication to arch_dup_mmap() which is only called on fork(). Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra Cc: Andy Lutomirski Cc: Andy Lutomirsky Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Dave Hansen Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Will Deacon Cc: aliguori@amazon.com Cc: dan.j.williams@intel.com Cc: hughd@google.com Cc: keescook@google.com Cc: kirill.shutemov@linux.intel.com Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar --- tools/testing/selftests/x86/ldt_gdt.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'tools/testing/selftests/x86') diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c index 66e5ce5b91f0..0304ffb714f2 100644 --- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -627,13 +627,10 @@ static void do_multicpu_tests(void) static int finish_exec_test(void) { /* - * In a sensible world, this would be check_invalid_segment(0, 1); - * For better or for worse, though, the LDT is inherited across exec. - * We can probably change this safely, but for now we test it. + * Older kernel versions did inherit the LDT on exec() which is + * wrong because exec() starts from a clean state. */ - check_valid_segment(0, 1, - AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB, - 42, true); + check_invalid_segment(0, 1); return nerrs ? 1 : 0; } -- cgit v1.2.3-59-g8ed1b