From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.outflux.net (smtp.outflux.net [IPv6:2001:19d0:2:6:c0de:0:736d:7470]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 78A8A1A04CD for ; Thu, 5 Mar 2015 08:12:44 +1100 (AEDT) From: Kees Cook To: akpm@linux-foundation.org Subject: [PATCH v4 04/10] mips: extract logic for mmap_rnd() Date: Wed, 4 Mar 2015 13:10:48 -0800 Message-Id: <1425503454-7531-5-git-send-email-keescook@chromium.org> In-Reply-To: <1425503454-7531-1-git-send-email-keescook@chromium.org> References: <1425503454-7531-1-git-send-email-keescook@chromium.org> Cc: linux-mips@linux-mips.org, Arun Chandran , Heiko Carstens , linux-kernel@vger.kernel.org, Min-Hua Chen , Paul Mackerras , Ismael Ripoll , Yann Droneaud , linux-s390@vger.kernel.org, Russell King , Andrey Ryabinin , x86@kernel.org, Hector Marco-Gisbert , Ingo Molnar , "David A. Long" , Catalin Marinas , Borislav Petkov , Ben Hutchings , Kees Cook , Will Deacon , linux-fsdevel@vger.kernel.org, Alexander Viro , Michael Holzheu , linux-arm-kernel@lists.infradead.org, Jeff Bailey , Paul Burton , Oleg Nesterov , Ralf Baechle , Andy Lutomirski , Vineeth Vijayan , Markos Chandras , =?UTF-8?q?Jan-Simon=20M=C3=B6ller?= , Martin Schwidefsky , linux390@de.ibm.com, linuxppc-dev@lists.ozlabs.org, Alex Smith List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , In preparation for splitting out ET_DYN ASLR, extract the mmap ASLR selection into a separate function. Signed-off-by: Kees Cook --- It seems the entropy gets smaller as the PAGE_SIZE increases. Is this intentional? --- arch/mips/mm/mmap.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c index f1baadd56e82..9a4f1f5c1f0e 100644 --- a/arch/mips/mm/mmap.c +++ b/arch/mips/mm/mmap.c @@ -142,18 +142,26 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp, addr0, len, pgoff, flags, DOWN); } +static unsigned long mmap_rnd(void) +{ + unsigned long rnd; + + rnd = (unsigned long)get_random_int(); + rnd <<= PAGE_SHIFT; + if (TASK_IS_32BIT_ADDR) + rnd &= 0xfffffful; + else + rnd &= 0xffffffful; + + return rnd; +} + void arch_pick_mmap_layout(struct mm_struct *mm) { unsigned long random_factor = 0UL; - if (current->flags & PF_RANDOMIZE) { - random_factor = get_random_int(); - random_factor = random_factor << PAGE_SHIFT; - if (TASK_IS_32BIT_ADDR) - random_factor &= 0xfffffful; - else - random_factor &= 0xffffffful; - } + if (current->flags & PF_RANDOMIZE) + random_factor = mmap_rnd(); if (mmap_is_legacy()) { mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; -- 1.9.1