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* [PATCH v6 00/14] Provide generic top-down mmap layout functions
@ 2019-08-08  6:17 Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 01/14] mm, fs: Move randomize_stack_top from fs to mm Alexandre Ghiti
                   ` (13 more replies)
  0 siblings, 14 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

This series introduces generic functions to make top-down mmap layout
easily accessible to architectures, in particular riscv which was
the initial goal of this series.
The generic implementation was taken from arm64 and used successively
by arm, mips and finally riscv.

Note that in addition the series fixes 2 issues:
- stack randomization was taken into account even if not necessary.
- [1] fixed an issue with mmap base which did not take into account
  randomization but did not report it to arm and mips, so by moving
  arm64 into a generic library, this problem is now fixed for both
  architectures.

This work is an effort to factorize architecture functions to avoid
code duplication and oversights as in [1].

[1]: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html

Changes in v6:
  - Do not handle sv48 as it will be correctly implemented later: assume
    64BIT <=> sv39.
  - Add acked-by from Paul

Changes in v5:
  - Fix [PATCH 11/14]
  - Rebase on top of v5.3rc2 and commit
    "riscv: kbuild: add virtual memory system selection"
  - [PATCH 14/14] now takes into account the various virtual memory systems

Changes in v4:
  - Make ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select ARCH_HAS_ELF_RANDOMIZE
    by default as suggested by Kees,
  - ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT depends on MMU and defines the
    functions needed by ARCH_HAS_ELF_RANDOMIZE => architectures that use
    the generic mmap topdown functions cannot have ARCH_HAS_ELF_RANDOMIZE
    selected without MMU, but I think it's ok since randomization without
    MMU does not add much security anyway.
  - There is no common API to determine if a process is 32b, so I came up with
    !IS_ENABLED(CONFIG_64BIT) || is_compat_task() in [PATCH v4 12/14].
  - Mention in the change log that x86 already takes care of not offseting mmap
    base address if the task does not want randomization.
  - Re-introduce a comment that should not have been removed.
  - Add Reviewed/Acked-By from Paul, Christoph and Kees, thank you for that.
  - I tried to minimize the changes from the commits in v3 in order to make
    easier the review of the v4, the commits changed or added are:
    - [PATCH v4 5/14]
    - [PATCH v4 8/14]
    - [PATCH v4 11/14]
    - [PATCH v4 12/14]
    - [PATCH v4 13/14]

Changes in v3:
  - Split into small patches to ease review as suggested by Christoph
    Hellwig and Kees Cook
  - Move help text of new config as a comment, as suggested by Christoph
  - Make new config depend on MMU, as suggested by Christoph

Changes in v2 as suggested by Christoph Hellwig:
  - Preparatory patch that moves randomize_stack_top
  - Fix duplicate config in riscv
  - Align #if defined on next line => this gives rise to a checkpatch
    warning. I found this pattern all around the tree, in the same proportion
    as the previous pattern which was less pretty:
    git grep -C 1 -n -P "^#if defined.+\|\|.*\\\\$" 

Alexandre Ghiti (14):
  mm, fs: Move randomize_stack_top from fs to mm
  arm64: Make use of is_compat_task instead of hardcoding this test
  arm64: Consider stack randomization for mmap base only when necessary
  arm64, mm: Move generic mmap layout functions to mm
  arm64, mm: Make randomization selected by generic topdown mmap layout
  arm: Properly account for stack randomization and stack guard gap
  arm: Use STACK_TOP when computing mmap base address
  arm: Use generic mmap top-down layout and brk randomization
  mips: Properly account for stack randomization and stack guard gap
  mips: Use STACK_TOP when computing mmap base address
  mips: Adjust brk randomization offset to fit generic version
  mips: Replace arch specific way to determine 32bit task with generic
    version
  mips: Use generic mmap top-down layout and brk randomization
  riscv: Make mmap allocation top-down by default

 arch/Kconfig                       |  11 +++
 arch/arm/Kconfig                   |   2 +-
 arch/arm/include/asm/processor.h   |   2 -
 arch/arm/kernel/process.c          |   5 --
 arch/arm/mm/mmap.c                 |  52 --------------
 arch/arm64/Kconfig                 |   2 +-
 arch/arm64/include/asm/processor.h |   2 -
 arch/arm64/kernel/process.c        |   8 ---
 arch/arm64/mm/mmap.c               |  72 -------------------
 arch/mips/Kconfig                  |   2 +-
 arch/mips/include/asm/processor.h  |   5 --
 arch/mips/mm/mmap.c                |  84 ----------------------
 arch/riscv/Kconfig                 |  12 ++++
 fs/binfmt_elf.c                    |  20 ------
 include/linux/mm.h                 |   2 +
 kernel/sysctl.c                    |   6 +-
 mm/util.c                          | 107 ++++++++++++++++++++++++++++-
 17 files changed, 138 insertions(+), 256 deletions(-)

-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 01/14] mm, fs: Move randomize_stack_top from fs to mm
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 02/14] arm64: Make use of is_compat_task instead of hardcoding this test Alexandre Ghiti
                   ` (12 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

This preparatory commit moves this function so that further introduction
of generic topdown mmap layout is contained only in mm/util.c.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 fs/binfmt_elf.c    | 20 --------------------
 include/linux/mm.h |  2 ++
 mm/util.c          | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index d4e11b2e04f6..cec3b4146440 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -670,26 +670,6 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex,
  * libraries.  There is no binary dependent code anywhere else.
  */
 
-#ifndef STACK_RND_MASK
-#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))	/* 8MB of VA */
-#endif
-
-static unsigned long randomize_stack_top(unsigned long stack_top)
-{
-	unsigned long random_variable = 0;
-
-	if (current->flags & PF_RANDOMIZE) {
-		random_variable = get_random_long();
-		random_variable &= STACK_RND_MASK;
-		random_variable <<= PAGE_SHIFT;
-	}
-#ifdef CONFIG_STACK_GROWSUP
-	return PAGE_ALIGN(stack_top) + random_variable;
-#else
-	return PAGE_ALIGN(stack_top) - random_variable;
-#endif
-}
-
 static int load_elf_binary(struct linux_binprm *bprm)
 {
 	struct file *interpreter = NULL; /* to shut gcc up */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0334ca97c584..ae0e5d241eb8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2351,6 +2351,8 @@ extern int install_special_mapping(struct mm_struct *mm,
 				   unsigned long addr, unsigned long len,
 				   unsigned long flags, struct page **pages);
 
+unsigned long randomize_stack_top(unsigned long stack_top);
+
 extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
 
 extern unsigned long mmap_region(struct file *file, unsigned long addr,
diff --git a/mm/util.c b/mm/util.c
index e6351a80f248..15a4fb0f5473 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -16,6 +16,8 @@
 #include <linux/hugetlb.h>
 #include <linux/vmalloc.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/elf.h>
+#include <linux/random.h>
 
 #include <linux/uaccess.h>
 
@@ -293,6 +295,26 @@ int vma_is_stack_for_current(struct vm_area_struct *vma)
 	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 }
 
+#ifndef STACK_RND_MASK
+#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))     /* 8MB of VA */
+#endif
+
+unsigned long randomize_stack_top(unsigned long stack_top)
+{
+	unsigned long random_variable = 0;
+
+	if (current->flags & PF_RANDOMIZE) {
+		random_variable = get_random_long();
+		random_variable &= STACK_RND_MASK;
+		random_variable <<= PAGE_SHIFT;
+	}
+#ifdef CONFIG_STACK_GROWSUP
+	return PAGE_ALIGN(stack_top) + random_variable;
+#else
+	return PAGE_ALIGN(stack_top) - random_variable;
+#endif
+}
+
 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 {
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 02/14] arm64: Make use of is_compat_task instead of hardcoding this test
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 01/14] mm, fs: Move randomize_stack_top from fs to mm Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 03/14] arm64: Consider stack randomization for mmap base only when necessary Alexandre Ghiti
                   ` (11 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

Each architecture has its own way to determine if a task is a compat task,
by using is_compat_task in arch_mmap_rnd, it allows more genericity and
then it prepares its moving to mm/.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/arm64/mm/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index b050641b5139..bb0140afed66 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -43,7 +43,7 @@ unsigned long arch_mmap_rnd(void)
 	unsigned long rnd;
 
 #ifdef CONFIG_COMPAT
-	if (test_thread_flag(TIF_32BIT))
+	if (is_compat_task())
 		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
 	else
 #endif
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 03/14] arm64: Consider stack randomization for mmap base only when necessary
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 01/14] mm, fs: Move randomize_stack_top from fs to mm Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 02/14] arm64: Make use of is_compat_task instead of hardcoding this test Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 04/14] arm64, mm: Move generic mmap layout functions to mm Alexandre Ghiti
                   ` (10 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

Do not offset mmap base address because of stack randomization if
current task does not want randomization.
Note that x86 already implements this behaviour.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/arm64/mm/mmap.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index bb0140afed66..e4acaead67de 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -54,7 +54,11 @@ unsigned long arch_mmap_rnd(void)
 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;
+	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)
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 04/14] arm64, mm: Move generic mmap layout functions to mm
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (2 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 03/14] arm64: Consider stack randomization for mmap base only when necessary Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout Alexandre Ghiti
                   ` (9 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti,
	Christoph Hellwig

arm64 handles top-down mmap layout in a way that can be easily reused
by other architectures, so make it available in mm.

It then introduces a new config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
that can be set by other architectures to benefit from those functions.
Note that this new config depends on MMU being enabled, if selected
without MMU support, a warning will be thrown.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/Kconfig                       | 10 ++++
 arch/arm64/Kconfig                 |  1 +
 arch/arm64/include/asm/processor.h |  2 -
 arch/arm64/mm/mmap.c               | 76 -----------------------------
 kernel/sysctl.c                    |  6 ++-
 mm/util.c                          | 78 +++++++++++++++++++++++++++++-
 6 files changed, 92 insertions(+), 81 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index a7b57dd42c26..a0bb6fa4d381 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -696,6 +696,16 @@ config HAVE_ARCH_COMPAT_MMAP_BASES
 	  and vice-versa 32-bit applications to call 64-bit mmap().
 	  Required for applications doing different bitness syscalls.
 
+# This allows to use a set of generic functions to determine mmap base
+# address by giving priority to top-down scheme only if the process
+# is not in legacy mode (compat task, unlimited stack size or
+# sysctl_legacy_va_layout).
+# Architecture that selects this option can provide its own version of:
+# - STACK_RND_MASK
+config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+	bool
+	depends on MMU
+
 config HAVE_COPY_THREAD_TLS
 	bool
 	help
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3adcec05b1f6..14a194e63458 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -72,6 +72,7 @@ config ARM64
 	select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
+	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 844e2964b0f5..65e2de00913f 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -281,8 +281,6 @@ static inline void spin_lock_prefetch(const void *ptr)
 		     "nop") : : "p" (ptr));
 }
 
-#define HAVE_ARCH_PICK_MMAP_LAYOUT
-
 #endif
 
 extern unsigned long __ro_after_init signal_minsigstksz; /* sigframe size */
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index e4acaead67de..3028bacbc4e9 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -20,82 +20,6 @@
 
 #include <asm/cputype.h>
 
-/*
- * Leave enough space between the mmap area and the stack to honour ulimit in
- * the face of randomisation.
- */
-#define MIN_GAP (SZ_128M)
-#define MAX_GAP	(STACK_TOP/6*5)
-
-static int mmap_is_legacy(struct rlimit *rlim_stack)
-{
-	if (current->personality & ADDR_COMPAT_LAYOUT)
-		return 1;
-
-	if (rlim_stack->rlim_cur == RLIM_INFINITY)
-		return 1;
-
-	return sysctl_legacy_va_layout;
-}
-
-unsigned long arch_mmap_rnd(void)
-{
-	unsigned long rnd;
-
-#ifdef CONFIG_COMPAT
-	if (is_compat_task())
-		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-	else
-#endif
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-	return rnd << PAGE_SHIFT;
-}
-
-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;
-	else if (gap > MAX_GAP)
-		gap = MAX_GAP;
-
-	return PAGE_ALIGN(STACK_TOP - gap - rnd);
-}
-
-/*
- * This function, called very early during the creation of a new process VM
- * image, sets up which VM layout function to use:
- */
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
-{
-	unsigned long random_factor = 0UL;
-
-	if (current->flags & PF_RANDOMIZE)
-		random_factor = arch_mmap_rnd();
-
-	/*
-	 * Fall back to the standard layout if the personality bit is set, or
-	 * if the expected stack growth is unlimited:
-	 */
-	if (mmap_is_legacy(rlim_stack)) {
-		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
-		mm->get_unmapped_area = arch_get_unmapped_area;
-	} else {
-		mm->mmap_base = mmap_base(random_factor, rlim_stack);
-		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
-	}
-}
-
 /*
  * You really shouldn't be using read() or write() on /dev/mem.  This might go
  * away in the future.
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 078950d9605b..00fcea236eba 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -264,7 +264,8 @@ extern struct ctl_table epoll_table[];
 extern struct ctl_table firmware_config_table[];
 #endif
 
-#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
+#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
+    defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)
 int sysctl_legacy_va_layout;
 #endif
 
@@ -1573,7 +1574,8 @@ static struct ctl_table vm_table[] = {
 		.proc_handler	= proc_dointvec,
 		.extra1		= SYSCTL_ZERO,
 	},
-#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT
+#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \
+    defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT)
 	{
 		.procname	= "legacy_va_layout",
 		.data		= &sysctl_legacy_va_layout,
diff --git a/mm/util.c b/mm/util.c
index 15a4fb0f5473..0781e5575cb3 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -17,7 +17,12 @@
 #include <linux/vmalloc.h>
 #include <linux/userfaultfd_k.h>
 #include <linux/elf.h>
+#include <linux/elf-randomize.h>
+#include <linux/personality.h>
 #include <linux/random.h>
+#include <linux/processor.h>
+#include <linux/sizes.h>
+#include <linux/compat.h>
 
 #include <linux/uaccess.h>
 
@@ -315,7 +320,78 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 #endif
 }
 
-#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
+#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
+#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+unsigned long arch_mmap_rnd(void)
+{
+	unsigned long rnd;
+
+#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
+	if (is_compat_task())
+		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
+	else
+#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
+		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+
+	return rnd << PAGE_SHIFT;
+}
+#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */
+
+static int mmap_is_legacy(struct rlimit *rlim_stack)
+{
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	if (rlim_stack->rlim_cur == RLIM_INFINITY)
+		return 1;
+
+	return sysctl_legacy_va_layout;
+}
+
+/*
+ * Leave enough space between the mmap area and the stack to honour ulimit in
+ * the face of randomisation.
+ */
+#define MIN_GAP		(SZ_128M)
+#define MAX_GAP		(STACK_TOP / 6 * 5)
+
+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;
+	else if (gap > MAX_GAP)
+		gap = MAX_GAP;
+
+	return PAGE_ALIGN(STACK_TOP - gap - rnd);
+}
+
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+{
+	unsigned long random_factor = 0UL;
+
+	if (current->flags & PF_RANDOMIZE)
+		random_factor = arch_mmap_rnd();
+
+	if (mmap_is_legacy(rlim_stack)) {
+		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
+		mm->get_unmapped_area = arch_get_unmapped_area;
+	} else {
+		mm->mmap_base = mmap_base(random_factor, rlim_stack);
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+	}
+}
+#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
 {
 	mm->mmap_base = TASK_UNMAPPED_BASE;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (3 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 04/14] arm64, mm: Move generic mmap layout functions to mm Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 06/14] arm: Properly account for stack randomization and stack guard gap Alexandre Ghiti
                   ` (8 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

This commits selects ARCH_HAS_ELF_RANDOMIZE when an arch uses the generic
topdown mmap layout functions so that this security feature is on by
default.

Note that this commit also removes the possibility for arm64 to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/Kconfig                |  1 +
 arch/arm64/Kconfig          |  1 -
 arch/arm64/kernel/process.c |  8 --------
 mm/util.c                   | 11 +++++++++--
 4 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index a0bb6fa4d381..d4c1f0551dfe 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -705,6 +705,7 @@ config HAVE_ARCH_COMPAT_MMAP_BASES
 config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 	bool
 	depends on MMU
+	select ARCH_HAS_ELF_RANDOMIZE
 
 config HAVE_COPY_THREAD_TLS
 	bool
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 14a194e63458..399f595ef852 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -16,7 +16,6 @@ config ARM64
 	select ARCH_HAS_DMA_MMAP_PGPROT
 	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
-	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index f674f28df663..8ddc2471b054 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -548,14 +548,6 @@ unsigned long arch_align_stack(unsigned long sp)
 	return sp & ~0xf;
 }
 
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	if (is_compat_task())
-		return randomize_page(mm->brk, SZ_32M);
-	else
-		return randomize_page(mm->brk, SZ_1G);
-}
-
 /*
  * Called from setup_new_exec() after (COMPAT_)SET_PERSONALITY.
  */
diff --git a/mm/util.c b/mm/util.c
index 0781e5575cb3..16f1e56e2996 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -321,7 +321,15 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 }
 
 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
-#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE
+unsigned long arch_randomize_brk(struct mm_struct *mm)
+{
+	/* Is the current task 32bit ? */
+	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
+		return randomize_page(mm->brk, SZ_32M);
+
+	return randomize_page(mm->brk, SZ_1G);
+}
+
 unsigned long arch_mmap_rnd(void)
 {
 	unsigned long rnd;
@@ -335,7 +343,6 @@ unsigned long arch_mmap_rnd(void)
 
 	return rnd << PAGE_SHIFT;
 }
-#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */
 
 static int mmap_is_legacy(struct rlimit *rlim_stack)
 {
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 06/14] arm: Properly account for stack randomization and stack guard gap
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (4 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 07/14] arm: Use STACK_TOP when computing mmap base address Alexandre Ghiti
                   ` (7 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

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@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.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


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 07/14] arm: Use STACK_TOP when computing mmap base address
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (5 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 06/14] arm: Properly account for stack randomization and stack guard gap Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 08/14] arm: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
                   ` (6 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

mmap base address must be computed wrt stack top address, using TASK_SIZE
is wrong since STACK_TOP and TASK_SIZE are not equivalent.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/arm/mm/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index bff3d00bda5b..0b94b674aa91 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -19,7 +19,7 @@
 
 /* gap between mmap and stack */
 #define MIN_GAP		(128*1024*1024UL)
-#define MAX_GAP		((TASK_SIZE)/6*5)
+#define MAX_GAP		((STACK_TOP)/6*5)
 #define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
 
 static int mmap_is_legacy(struct rlimit *rlim_stack)
@@ -51,7 +51,7 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+	return PAGE_ALIGN(STACK_TOP - gap - rnd);
 }
 
 /*
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 08/14] arm: Use generic mmap top-down layout and brk randomization
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (6 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 07/14] arm: Use STACK_TOP when computing mmap base address Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap Alexandre Ghiti
                   ` (5 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

arm uses a top-down mmap layout by default that exactly fits the generic
functions, so get rid of arch specific code and use the generic version
by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.

As ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects ARCH_HAS_ELF_RANDOMIZE,
use the generic version of arch_randomize_brk since it also fits.
Note that this commit also removes the possibility for arm to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.

Note that it is safe to remove STACK_RND_MASK since it matches the default
value.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/arm/Kconfig                 |  2 +-
 arch/arm/include/asm/processor.h |  2 --
 arch/arm/kernel/process.c        |  5 ---
 arch/arm/mm/mmap.c               | 62 --------------------------------
 4 files changed, 1 insertion(+), 70 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 33b00579beff..81b08b027e4e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -7,7 +7,6 @@ config ARM
 	select ARCH_HAS_BINFMT_FLAT
 	select ARCH_HAS_DEBUG_VIRTUAL if MMU
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
-	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_KEEPINITRD
 	select ARCH_HAS_KCOV
@@ -30,6 +29,7 @@ config ARM
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_USE_BUILTIN_BSWAP
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
 	select BUILDTIME_EXTABLE_SORT if MMU
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 20c2f42454b8..614bf829e454 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -140,8 +140,6 @@ static inline void prefetchw(const void *ptr)
 #endif
 #endif
 
-#define HAVE_ARCH_PICK_MMAP_LAYOUT
-
 #endif
 
 #endif /* __ASM_ARM_PROCESSOR_H */
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f934a6739fc0..9485acc520a4 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -319,11 +319,6 @@ unsigned long get_wchan(struct task_struct *p)
 	return 0;
 }
 
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	return randomize_page(mm->brk, 0x02000000);
-}
-
 #ifdef CONFIG_MMU
 #ifdef CONFIG_KUSER_HELPERS
 /*
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 0b94b674aa91..b8d912ac9e61 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -17,43 +17,6 @@
 	((((addr)+SHMLBA-1)&~(SHMLBA-1)) +	\
 	 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
 
-/* gap between mmap and stack */
-#define MIN_GAP		(128*1024*1024UL)
-#define MAX_GAP		((STACK_TOP)/6*5)
-#define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
-
-static int mmap_is_legacy(struct rlimit *rlim_stack)
-{
-	if (current->personality & ADDR_COMPAT_LAYOUT)
-		return 1;
-
-	if (rlim_stack->rlim_cur == RLIM_INFINITY)
-		return 1;
-
-	return sysctl_legacy_va_layout;
-}
-
-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;
-	else if (gap > MAX_GAP)
-		gap = MAX_GAP;
-
-	return PAGE_ALIGN(STACK_TOP - gap - rnd);
-}
-
 /*
  * We need to ensure that shared mappings are correctly aligned to
  * avoid aliasing issues with VIPT caches.  We need to ensure that
@@ -181,31 +144,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
 	return addr;
 }
 
-unsigned long arch_mmap_rnd(void)
-{
-	unsigned long rnd;
-
-	rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-
-	return rnd << PAGE_SHIFT;
-}
-
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
-{
-	unsigned long random_factor = 0UL;
-
-	if (current->flags & PF_RANDOMIZE)
-		random_factor = arch_mmap_rnd();
-
-	if (mmap_is_legacy(rlim_stack)) {
-		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
-		mm->get_unmapped_area = arch_get_unmapped_area;
-	} else {
-		mm->mmap_base = mmap_base(random_factor, rlim_stack);
-		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
-	}
-}
-
 /*
  * You really shouldn't be using read() or write() on /dev/mem.  This
  * might go away in the future.
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (7 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 08/14] arm: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  9:16   ` Sergei Shtylyov
  2019-08-08  6:17 ` [PATCH v6 10/14] mips: Use STACK_TOP when computing mmap base address Alexandre Ghiti
                   ` (4 subsequent siblings)
  13 siblings, 1 reply; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

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@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/mm/mmap.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index d79f2b432318..f5c778113384 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -21,8 +21,9 @@ unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
 
 /* 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)
 {
@@ -38,6 +39,15 @@ 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


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 10/14] mips: Use STACK_TOP when computing mmap base address
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (8 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version Alexandre Ghiti
                   ` (3 subsequent siblings)
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

mmap base address must be computed wrt stack top address, using TASK_SIZE
is wrong since STACK_TOP and TASK_SIZE are not equivalent.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/mm/mmap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index f5c778113384..a7e84b2e71d7 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -22,7 +22,7 @@ EXPORT_SYMBOL(shm_align_mask);
 
 /* gap between mmap and stack */
 #define MIN_GAP		(128*1024*1024UL)
-#define MAX_GAP		((TASK_SIZE)/6*5)
+#define MAX_GAP		((STACK_TOP)/6*5)
 #define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
 
 static int mmap_is_legacy(struct rlimit *rlim_stack)
@@ -54,7 +54,7 @@ static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
 	else if (gap > MAX_GAP)
 		gap = MAX_GAP;
 
-	return PAGE_ALIGN(TASK_SIZE - gap - rnd);
+	return PAGE_ALIGN(STACK_TOP - gap - rnd);
 }
 
 #define COLOUR_ALIGN(addr, pgoff)				\
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (9 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 10/14] mips: Use STACK_TOP when computing mmap base address Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  9:19   ` Sergei Shtylyov
  2019-08-08  6:17 ` [PATCH v6 12/14] mips: Replace arch specific way to determine 32bit task with " Alexandre Ghiti
                   ` (2 subsequent siblings)
  13 siblings, 1 reply; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

This commit simply bumps up to 32MB and 1GB the random offset
of brk, compared to 8MB and 256MB, for 32bit and 64bit respectively.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/mm/mmap.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index a7e84b2e71d7..ff6ab87e9c56 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -16,6 +16,7 @@
 #include <linux/random.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
+#include <linux/sizes.h>
 
 unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
@@ -189,11 +190,11 @@ static inline unsigned long brk_rnd(void)
 	unsigned long rnd = get_random_long();
 
 	rnd = rnd << PAGE_SHIFT;
-	/* 8MB for 32bit, 256MB for 64bit */
+	/* 32MB for 32bit, 1GB for 64bit */
 	if (TASK_IS_32BIT_ADDR)
-		rnd = rnd & 0x7ffffful;
+		rnd = rnd & (SZ_32M - 1);
 	else
-		rnd = rnd & 0xffffffful;
+		rnd = rnd & (SZ_1G - 1);
 
 	return rnd;
 }
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 12/14] mips: Replace arch specific way to determine 32bit task with generic version
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (10 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version Alexandre Ghiti
@ 2019-08-08  6:17 ` " Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 13/14] mips: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 14/14] riscv: Make mmap allocation top-down by default Alexandre Ghiti
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

Mips uses TASK_IS_32BIT_ADDR to determine if a task is 32bit, but
this define is mips specific and other arches do not have it: instead,
use !IS_ENABLED(CONFIG_64BIT) || is_compat_task() condition.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/mm/mmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index ff6ab87e9c56..d5106c26ac6a 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -17,6 +17,7 @@
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
 #include <linux/sizes.h>
+#include <linux/compat.h>
 
 unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
@@ -191,7 +192,7 @@ static inline unsigned long brk_rnd(void)
 
 	rnd = rnd << PAGE_SHIFT;
 	/* 32MB for 32bit, 1GB for 64bit */
-	if (TASK_IS_32BIT_ADDR)
+	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
 		rnd = rnd & (SZ_32M - 1);
 	else
 		rnd = rnd & (SZ_1G - 1);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 13/14] mips: Use generic mmap top-down layout and brk randomization
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (11 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 12/14] mips: Replace arch specific way to determine 32bit task with " Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  2019-08-08  6:17 ` [PATCH v6 14/14] riscv: Make mmap allocation top-down by default Alexandre Ghiti
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

mips uses a top-down layout by default that exactly fits the generic
functions, so get rid of arch specific code and use the generic version
by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.

As ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects ARCH_HAS_ELF_RANDOMIZE,
use the generic version of arch_randomize_brk since it also fits.

Note that this commit also removes the possibility for mips to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/mips/Kconfig                 |  2 +-
 arch/mips/include/asm/processor.h |  5 --
 arch/mips/mm/mmap.c               | 96 -------------------------------
 3 files changed, 1 insertion(+), 102 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d50fafd7bf3a..4e85d7d2cf1a 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -5,7 +5,6 @@ config MIPS
 	select ARCH_32BIT_OFF_T if !64BIT
 	select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
 	select ARCH_CLOCKSOURCE_DATA
-	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
 	select ARCH_SUPPORTS_UPROBES
@@ -13,6 +12,7 @@ config MIPS
 	select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_USE_QUEUED_SPINLOCKS
+	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
 	select CLONE_BACKWARDS
diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index aca909bd7841..fba18d4a9190 100644
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -29,11 +29,6 @@
 
 extern unsigned int vced_count, vcei_count;
 
-/*
- * MIPS does have an arch_pick_mmap_layout()
- */
-#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
-
 #ifdef CONFIG_32BIT
 #ifdef CONFIG_KVM_GUEST
 /* User space process size is limited to 1GB in KVM Guest Mode */
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index d5106c26ac6a..00fe90c6db3e 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -16,49 +16,10 @@
 #include <linux/random.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
-#include <linux/sizes.h>
-#include <linux/compat.h>
 
 unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
 
-/* gap between mmap and stack */
-#define MIN_GAP		(128*1024*1024UL)
-#define MAX_GAP		((STACK_TOP)/6*5)
-#define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
-
-static int mmap_is_legacy(struct rlimit *rlim_stack)
-{
-	if (current->personality & ADDR_COMPAT_LAYOUT)
-		return 1;
-
-	if (rlim_stack->rlim_cur == RLIM_INFINITY)
-		return 1;
-
-	return sysctl_legacy_va_layout;
-}
-
-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;
-	else if (gap > MAX_GAP)
-		gap = MAX_GAP;
-
-	return PAGE_ALIGN(STACK_TOP - gap - rnd);
-}
-
 #define COLOUR_ALIGN(addr, pgoff)				\
 	((((addr) + shm_align_mask) & ~shm_align_mask) +	\
 	 (((pgoff) << PAGE_SHIFT) & shm_align_mask))
@@ -156,63 +117,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
 			addr0, len, pgoff, flags, DOWN);
 }
 
-unsigned long arch_mmap_rnd(void)
-{
-	unsigned long rnd;
-
-#ifdef CONFIG_COMPAT
-	if (TASK_IS_32BIT_ADDR)
-		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-	else
-#endif /* CONFIG_COMPAT */
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-
-	return rnd << PAGE_SHIFT;
-}
-
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
-{
-	unsigned long random_factor = 0UL;
-
-	if (current->flags & PF_RANDOMIZE)
-		random_factor = arch_mmap_rnd();
-
-	if (mmap_is_legacy(rlim_stack)) {
-		mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
-		mm->get_unmapped_area = arch_get_unmapped_area;
-	} else {
-		mm->mmap_base = mmap_base(random_factor, rlim_stack);
-		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
-	}
-}
-
-static inline unsigned long brk_rnd(void)
-{
-	unsigned long rnd = get_random_long();
-
-	rnd = rnd << PAGE_SHIFT;
-	/* 32MB for 32bit, 1GB for 64bit */
-	if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
-		rnd = rnd & (SZ_32M - 1);
-	else
-		rnd = rnd & (SZ_1G - 1);
-
-	return rnd;
-}
-
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-	unsigned long base = mm->brk;
-	unsigned long ret;
-
-	ret = PAGE_ALIGN(base + brk_rnd());
-
-	if (ret < mm->brk)
-		return mm->brk;
-
-	return ret;
-}
-
 bool __virt_addr_valid(const volatile void *kaddr)
 {
 	unsigned long vaddr = (unsigned long)kaddr;
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH v6 14/14] riscv: Make mmap allocation top-down by default
  2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
                   ` (12 preceding siblings ...)
  2019-08-08  6:17 ` [PATCH v6 13/14] mips: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
@ 2019-08-08  6:17 ` Alexandre Ghiti
  13 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-08  6:17 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm, Alexandre Ghiti

In order to avoid wasting user address space by using bottom-up mmap
allocation scheme, prefer top-down scheme when possible.

Before:
root@qemuriscv64:~# cat /proc/self/maps
00010000-00016000 r-xp 00000000 fe:00 6389       /bin/cat.coreutils
00016000-00017000 r--p 00005000 fe:00 6389       /bin/cat.coreutils
00017000-00018000 rw-p 00006000 fe:00 6389       /bin/cat.coreutils
00018000-00039000 rw-p 00000000 00:00 0          [heap]
1555556000-155556d000 r-xp 00000000 fe:00 7193   /lib/ld-2.28.so
155556d000-155556e000 r--p 00016000 fe:00 7193   /lib/ld-2.28.so
155556e000-155556f000 rw-p 00017000 fe:00 7193   /lib/ld-2.28.so
155556f000-1555570000 rw-p 00000000 00:00 0
1555570000-1555572000 r-xp 00000000 00:00 0      [vdso]
1555574000-1555576000 rw-p 00000000 00:00 0
1555576000-1555674000 r-xp 00000000 fe:00 7187   /lib/libc-2.28.so
1555674000-1555678000 r--p 000fd000 fe:00 7187   /lib/libc-2.28.so
1555678000-155567a000 rw-p 00101000 fe:00 7187   /lib/libc-2.28.so
155567a000-15556a0000 rw-p 00000000 00:00 0
3fffb90000-3fffbb1000 rw-p 00000000 00:00 0      [stack]

After:
root@qemuriscv64:~# cat /proc/self/maps
00010000-00016000 r-xp 00000000 fe:00 6389       /bin/cat.coreutils
00016000-00017000 r--p 00005000 fe:00 6389       /bin/cat.coreutils
00017000-00018000 rw-p 00006000 fe:00 6389       /bin/cat.coreutils
2de81000-2dea2000 rw-p 00000000 00:00 0          [heap]
3ff7eb6000-3ff7ed8000 rw-p 00000000 00:00 0
3ff7ed8000-3ff7fd6000 r-xp 00000000 fe:00 7187   /lib/libc-2.28.so
3ff7fd6000-3ff7fda000 r--p 000fd000 fe:00 7187   /lib/libc-2.28.so
3ff7fda000-3ff7fdc000 rw-p 00101000 fe:00 7187   /lib/libc-2.28.so
3ff7fdc000-3ff7fe2000 rw-p 00000000 00:00 0
3ff7fe4000-3ff7fe6000 r-xp 00000000 00:00 0      [vdso]
3ff7fe6000-3ff7ffd000 r-xp 00000000 fe:00 7193   /lib/ld-2.28.so
3ff7ffd000-3ff7ffe000 r--p 00016000 fe:00 7193   /lib/ld-2.28.so
3ff7ffe000-3ff7fff000 rw-p 00017000 fe:00 7193   /lib/ld-2.28.so
3ff7fff000-3ff8000000 rw-p 00000000 00:00 0
3fff888000-3fff8a9000 rw-p 00000000 00:00 0      [stack]

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Paul Walmsley <paul.walmsley@sifive.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
---
 arch/riscv/Kconfig | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 59a4727ecd6c..87dc5370becb 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -54,6 +54,18 @@ config RISCV
 	select EDAC_SUPPORT
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
+	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
+	select HAVE_ARCH_MMAP_RND_BITS
+
+config ARCH_MMAP_RND_BITS_MIN
+	default 18 if 64BIT
+	default 8
+
+# max bits determined by the following formula:
+#  VA_BITS - PAGE_SHIFT - 3
+config ARCH_MMAP_RND_BITS_MAX
+	default 24 if 64BIT # SV39 based
+	default 17
 
 config MMU
 	def_bool y
-- 
2.20.1


^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap
  2019-08-08  6:17 ` [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap Alexandre Ghiti
@ 2019-08-08  9:16   ` Sergei Shtylyov
  2019-08-09  9:44     ` Alexandre Ghiti
  0 siblings, 1 reply; 19+ messages in thread
From: Sergei Shtylyov @ 2019-08-08  9:16 UTC (permalink / raw)
  To: Alexandre Ghiti, Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm

Hello!

On 08.08.2019 9:17, Alexandre Ghiti wrote:

> 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@ghiti.fr>
> Acked-by: Kees Cook <keescook@chromium.org>
> Acked-by: Paul Burton <paul.burton@mips.com>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>   arch/mips/mm/mmap.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
> index d79f2b432318..f5c778113384 100644
> --- a/arch/mips/mm/mmap.c
> +++ b/arch/mips/mm/mmap.c
> @@ -21,8 +21,9 @@ unsigned long shm_align_mask = PAGE_SIZE - 1;	/* Sane caches */
>   EXPORT_SYMBOL(shm_align_mask);
>   
>   /* 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)

    Could add spaces around *, while touching this anyway? And parens
around TASK_SIZE shouldn't be needed...

> +#define STACK_RND_MASK	(0x7ff >> (PAGE_SHIFT - 12))
>   
>   static int mmap_is_legacy(struct rlimit *rlim_stack)
>   {
> @@ -38,6 +39,15 @@ 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);

    Parens not needed here.

> +
> +	/* Values close to RLIM_INFINITY can overflow. */
> +	if (gap + pad > gap)
> +		gap += pad;
>   
>   	if (gap < MIN_GAP)
>   		gap = MIN_GAP;
> 


^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version
  2019-08-08  6:17 ` [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version Alexandre Ghiti
@ 2019-08-08  9:19   ` Sergei Shtylyov
  2019-08-09  9:45     ` Alexandre Ghiti
  0 siblings, 1 reply; 19+ messages in thread
From: Sergei Shtylyov @ 2019-08-08  9:19 UTC (permalink / raw)
  To: Alexandre Ghiti, Andrew Morton
  Cc: Paul Walmsley, Luis Chamberlain, Christoph Hellwig, Russell King,
	Catalin Marinas, Will Deacon, Ralf Baechle, Paul Burton,
	James Hogan, Palmer Dabbelt, Albert Ou, Alexander Viro,
	Kees Cook, linux-kernel, linux-arm-kernel, linux-mips,
	linux-riscv, linux-fsdevel, linux-mm

Hello!

On 08.08.2019 9:17, Alexandre Ghiti wrote:

> This commit simply bumps up to 32MB and 1GB the random offset
> of brk, compared to 8MB and 256MB, for 32bit and 64bit respectively.
> 
> Suggested-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> Acked-by: Paul Burton <paul.burton@mips.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> ---
>   arch/mips/mm/mmap.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
> index a7e84b2e71d7..ff6ab87e9c56 100644
> --- a/arch/mips/mm/mmap.c
> +++ b/arch/mips/mm/mmap.c
[...]
> @@ -189,11 +190,11 @@ static inline unsigned long brk_rnd(void)
>   	unsigned long rnd = get_random_long();
>   
>   	rnd = rnd << PAGE_SHIFT;
> -	/* 8MB for 32bit, 256MB for 64bit */
> +	/* 32MB for 32bit, 1GB for 64bit */
>   	if (TASK_IS_32BIT_ADDR)
> -		rnd = rnd & 0x7ffffful;
> +		rnd = rnd & (SZ_32M - 1);
>   	else
> -		rnd = rnd & 0xffffffful;
> +		rnd = rnd & (SZ_1G - 1);

    Why not make these 'rnd &= SZ_* - 1', while at it anyways?

[...]

MBR, Sergei

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap
  2019-08-08  9:16   ` Sergei Shtylyov
@ 2019-08-09  9:44     ` Alexandre Ghiti
  0 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-09  9:44 UTC (permalink / raw)
  To: Sergei Shtylyov, Andrew Morton
  Cc: Albert Ou, Kees Cook, linux-mm, Catalin Marinas, Palmer Dabbelt,
	Will Deacon, Russell King, Ralf Baechle, linux-kernel,
	linux-fsdevel, Luis Chamberlain, Paul Burton, Paul Walmsley,
	James Hogan, linux-riscv, linux-mips, Christoph Hellwig,
	linux-arm-kernel, Alexander Viro

On 8/8/19 11:16 AM, Sergei Shtylyov wrote:
> Hello!
>
> On 08.08.2019 9:17, Alexandre Ghiti wrote:
>
>> 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@ghiti.fr>
>> Acked-by: Kees Cook <keescook@chromium.org>
>> Acked-by: Paul Burton <paul.burton@mips.com>
>> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
>> ---
>>   arch/mips/mm/mmap.c | 14 ++++++++++++--
>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
>> index d79f2b432318..f5c778113384 100644
>> --- a/arch/mips/mm/mmap.c
>> +++ b/arch/mips/mm/mmap.c
>> @@ -21,8 +21,9 @@ unsigned long shm_align_mask = PAGE_SIZE - 1;    /* 
>> Sane caches */
>>   EXPORT_SYMBOL(shm_align_mask);
>>     /* 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)
>
>    Could add spaces around *, while touching this anyway? And parens
> around TASK_SIZE shouldn't be needed...
>

I did not fix checkpatch warnings here since this code gets removed 
afterwards.


>> +#define STACK_RND_MASK    (0x7ff >> (PAGE_SHIFT - 12))
>>     static int mmap_is_legacy(struct rlimit *rlim_stack)
>>   {
>> @@ -38,6 +39,15 @@ 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);
>
>    Parens not needed here.


Belt and braces approach here as I'm never sure about priorities.

Thanks for your time,

Alex


>
>> +
>> +    /* Values close to RLIM_INFINITY can overflow. */
>> +    if (gap + pad > gap)
>> +        gap += pad;
>>         if (gap < MIN_GAP)
>>           gap = MIN_GAP;
>>
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

^ permalink raw reply	[flat|nested] 19+ messages in thread

* Re: [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version
  2019-08-08  9:19   ` Sergei Shtylyov
@ 2019-08-09  9:45     ` Alexandre Ghiti
  0 siblings, 0 replies; 19+ messages in thread
From: Alexandre Ghiti @ 2019-08-09  9:45 UTC (permalink / raw)
  To: Sergei Shtylyov, Andrew Morton
  Cc: Albert Ou, Kees Cook, linux-mm, Catalin Marinas, Palmer Dabbelt,
	Will Deacon, Russell King, Ralf Baechle, linux-kernel,
	linux-fsdevel, Luis Chamberlain, Paul Burton, Paul Walmsley,
	James Hogan, linux-riscv, linux-mips, Christoph Hellwig,
	linux-arm-kernel, Alexander Viro

On 8/8/19 11:19 AM, Sergei Shtylyov wrote:
> Hello!
>
> On 08.08.2019 9:17, Alexandre Ghiti wrote:
>
>> This commit simply bumps up to 32MB and 1GB the random offset
>> of brk, compared to 8MB and 256MB, for 32bit and 64bit respectively.
>>
>> Suggested-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
>> Acked-by: Paul Burton <paul.burton@mips.com>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
>> ---
>>   arch/mips/mm/mmap.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
>> index a7e84b2e71d7..ff6ab87e9c56 100644
>> --- a/arch/mips/mm/mmap.c
>> +++ b/arch/mips/mm/mmap.c
> [...]
>> @@ -189,11 +190,11 @@ static inline unsigned long brk_rnd(void)
>>       unsigned long rnd = get_random_long();
>>         rnd = rnd << PAGE_SHIFT;
>> -    /* 8MB for 32bit, 256MB for 64bit */
>> +    /* 32MB for 32bit, 1GB for 64bit */
>>       if (TASK_IS_32BIT_ADDR)
>> -        rnd = rnd & 0x7ffffful;
>> +        rnd = rnd & (SZ_32M - 1);
>>       else
>> -        rnd = rnd & 0xffffffful;
>> +        rnd = rnd & (SZ_1G - 1);
>
>    Why not make these 'rnd &= SZ_* - 1', while at it anyways?


You're right, I could have. Again, this code gets removed afterwards, so 
I think it's ok
to leave it as is.

Anyway, thanks for your remarks Sergei !

Alex


>
> [...]
>
> MBR, Sergei
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, back to index

Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-08-08  6:17 [PATCH v6 00/14] Provide generic top-down mmap layout functions Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 01/14] mm, fs: Move randomize_stack_top from fs to mm Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 02/14] arm64: Make use of is_compat_task instead of hardcoding this test Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 03/14] arm64: Consider stack randomization for mmap base only when necessary Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 04/14] arm64, mm: Move generic mmap layout functions to mm Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 06/14] arm: Properly account for stack randomization and stack guard gap Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 07/14] arm: Use STACK_TOP when computing mmap base address Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 08/14] arm: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap Alexandre Ghiti
2019-08-08  9:16   ` Sergei Shtylyov
2019-08-09  9:44     ` Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 10/14] mips: Use STACK_TOP when computing mmap base address Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 11/14] mips: Adjust brk randomization offset to fit generic version Alexandre Ghiti
2019-08-08  9:19   ` Sergei Shtylyov
2019-08-09  9:45     ` Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 12/14] mips: Replace arch specific way to determine 32bit task with " Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 13/14] mips: Use generic mmap top-down layout and brk randomization Alexandre Ghiti
2019-08-08  6:17 ` [PATCH v6 14/14] riscv: Make mmap allocation top-down by default Alexandre Ghiti

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