From 47ac5484fd961420e5ec0bb5b972fde381f57365 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 15 Aug 2017 17:39:52 +0200 Subject: [PATCH] x86: Fix norandmaps/ADDR_NO_RANDOMIZE Documentation/admin-guide/kernel-parameters.txt says: norandmaps Don't use address space randomization. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space but it doesn't work because arch_rnd() which is used to randomize mm->mmap_base returns a random value unconditionally. And as Kirill pointed out, ADDR_NO_RANDOMIZE is broken by the same reason. Just shift the PF_RANDOMIZE check from arch_mmap_rnd() to arch_rnd(). Fixes: 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for 32-bit mmap()") Signed-off-by: Oleg Nesterov Signed-off-by: Thomas Gleixner Acked-by: Kirill A. Shutemov Acked-by: Cyrill Gorcunov Reviewed-by: Dmitry Safonov Cc: stable@vger.kernel.org Cc: Andy Lutomirski Cc: Andrew Morton Cc: Borislav Petkov Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20170815153952.GA1076@redhat.com --- arch/x86/mm/mmap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 229d04a83f85..c94df122815a 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -79,13 +79,13 @@ static int mmap_is_legacy(void) static unsigned long arch_rnd(unsigned int rndbits) { + if (!(current->flags & PF_RANDOMIZE)) + return 0; return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; } unsigned long arch_mmap_rnd(void) { - if (!(current->flags & PF_RANDOMIZE)) - return 0; return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits); } -- 2.39.2