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From: Ali Saidi <alisaidi@amazon.com>
To: <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>, <x86@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Ali Saidi <alisaidi@amazon.com>,
	Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@alien8.de>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Will Deacon <will.deacon@arm.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Anthony Liguori <aliguori@amazon.com>
Subject: [PATCH 1/2] arm64/mmap: handle worst-case heap randomization in mmap_base
Date: Tue, 12 Mar 2019 17:32:47 +0000	[thread overview]
Message-ID: <20190312173248.13490-2-alisaidi@amazon.com> (raw)
In-Reply-To: <20190312173248.13490-1-alisaidi@amazon.com>

Increase mmap_base by the worst-case brk randomization so that
the stack and heap remain apart.

In Linux 4.13 a change was committed that special cased the kernel ELF
loader when the loader is invoked directly (eab09532d400; binfmt_elf: use
ELF_ET_DYN_BASE only for PIE). Generally, the loader isn’t invoked
directly and this issue is limited to cases where it is, (e.g to set a
non-inheritable LD_LIBRARY_PATH, testing new versions of the loader). In
those rare cases, the loader doesn't take into account the amount of brk
randomization that will be applied by arch_randomize_brk(). This can
lead to the stack and heap being arbitrarily close to each other.

Signed-off-by: Ali Saidi <alisaidi@amazon.com>

---
 arch/arm64/mm/mmap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 842c8a5fcd53..0778f7ba8306 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -67,6 +67,14 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 	unsigned long gap = rlim_stack->rlim_cur;
 	unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap;
 
+	/* Provide space for randomization when randomize_va_space == 2 and
+	 * ld-linux.so is called directly. Values from arch_randomize_brk()
+	 */
+	if (test_thread_flag(TIF_32BIT))
+		pad += SZ_32M;
+	else
+		pad += SZ_1G;
+
 	/* Values close to RLIM_INFINITY can overflow. */
 	if (gap + pad > gap)
 		gap += pad;
-- 
2.15.3.AMZN


WARNING: multiple messages have this Message-ID (diff)
From: Ali Saidi <alisaidi@amazon.com>
To: <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>, <x86@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Will Deacon <will.deacon@arm.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Andy Lutomirski <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ali Saidi <alisaidi@amazon.com>,
	Anthony Liguori <aliguori@amazon.com>
Subject: [PATCH 1/2] arm64/mmap: handle worst-case heap randomization in mmap_base
Date: Tue, 12 Mar 2019 17:32:47 +0000	[thread overview]
Message-ID: <20190312173248.13490-2-alisaidi@amazon.com> (raw)
In-Reply-To: <20190312173248.13490-1-alisaidi@amazon.com>

Increase mmap_base by the worst-case brk randomization so that
the stack and heap remain apart.

In Linux 4.13 a change was committed that special cased the kernel ELF
loader when the loader is invoked directly (eab09532d400; binfmt_elf: use
ELF_ET_DYN_BASE only for PIE). Generally, the loader isn’t invoked
directly and this issue is limited to cases where it is, (e.g to set a
non-inheritable LD_LIBRARY_PATH, testing new versions of the loader). In
those rare cases, the loader doesn't take into account the amount of brk
randomization that will be applied by arch_randomize_brk(). This can
lead to the stack and heap being arbitrarily close to each other.

Signed-off-by: Ali Saidi <alisaidi@amazon.com>

---
 arch/arm64/mm/mmap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 842c8a5fcd53..0778f7ba8306 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -67,6 +67,14 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 	unsigned long gap = rlim_stack->rlim_cur;
 	unsigned long pad = (STACK_RND_MASK << PAGE_SHIFT) + stack_guard_gap;
 
+	/* Provide space for randomization when randomize_va_space == 2 and
+	 * ld-linux.so is called directly. Values from arch_randomize_brk()
+	 */
+	if (test_thread_flag(TIF_32BIT))
+		pad += SZ_32M;
+	else
+		pad += SZ_1G;
+
 	/* Values close to RLIM_INFINITY can overflow. */
 	if (gap + pad > gap)
 		gap += pad;
-- 
2.15.3.AMZN


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2019-03-12 17:33 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-12 17:32 [PATCH 0/2] handle worst-case heap randomization in mmap_base Ali Saidi
2019-03-12 17:32 ` Ali Saidi
2019-03-12 17:32 ` Ali Saidi [this message]
2019-03-12 17:32   ` [PATCH 1/2] arm64/mmap: " Ali Saidi
2019-03-12 17:32 ` [PATCH 2/2] x86/mmap: " Ali Saidi
2019-03-12 17:32   ` Ali Saidi
2019-03-13 16:25   ` Dave Hansen
2019-03-13 16:25     ` Dave Hansen
2019-03-17 15:52     ` Saidi, Ali
2019-03-17 15:52       ` Saidi, Ali
2019-03-13 22:58   ` Kees Cook
2019-03-13 22:58     ` Kees Cook
2019-03-27 19:51     ` Kees Cook
2019-03-27 19:51       ` Kees Cook
2019-04-15 16:03       ` Saidi, Ali
2019-04-15 16:03         ` Saidi, Ali
2019-04-19  8:51         ` Ingo Molnar
2019-04-19  8:51           ` Ingo Molnar
2019-04-19 15:00           ` Kees Cook
2019-04-19 15:00             ` Kees Cook
2019-03-21 14:09   ` Thomas Gleixner
2019-03-21 14:09     ` Thomas Gleixner
2019-03-26  2:13     ` Saidi, Ali
2019-03-26  2:13       ` Saidi, Ali
2019-03-26  8:43       ` Thomas Gleixner
2019-03-26  8:43         ` Thomas Gleixner

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