linux-kernel - [PATCH v5 06/14] arm: Properly account for stack randomization and stack guard gap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190730055113.23635-7-alex@ghiti.fr>
Date:   Tue, 30 Jul 2019 01:51:05 -0400
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Christoph Hellwig <hch@....de>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mips@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        Alexandre Ghiti <alex@...ti.fr>
Subject: [PATCH v5 06/14] arm: Properly account for stack randomization and stack guard gap

This commit takes care of stack randomization and stack guard gap when
computing mmap base address and checks if the task asked for randomization.
This fixes the problem uncovered and not fixed for arm here:
https://lkml.kernel.org/r/20170622200033.25714-1-riel@redhat.com

Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
Acked-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
---
 arch/arm/mm/mmap.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index f866870db749..bff3d00bda5b 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -18,8 +18,9 @@
 	 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
 
 /* gap between mmap and stack */
-#define MIN_GAP (128*1024*1024UL)
-#define MAX_GAP ((TASK_SIZE)/6*5)
+#define MIN_GAP		(128*1024*1024UL)
+#define MAX_GAP		((TASK_SIZE)/6*5)
+#define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
 
 static int mmap_is_legacy(struct rlimit *rlim_stack)
 {
@@ -35,6 +36,15 @@ static int mmap_is_legacy(struct rlimit *rlim_stack)
 static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 {
 	unsigned long gap = rlim_stack->rlim_cur;
+	unsigned long pad = stack_guard_gap;
+
+	/* Account for stack randomization if necessary */
+	if (current->flags & PF_RANDOMIZE)
+		pad += (STACK_RND_MASK << PAGE_SHIFT);
+
+	/* Values close to RLIM_INFINITY can overflow. */
+	if (gap + pad > gap)
+		gap += pad;
 
 	if (gap < MIN_GAP)
 		gap = MIN_GAP;
-- 
2.20.1