[PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[Alexandre Ghiti]

Hi Andrew,

This is simply a rebase on top of next-20190719, where I added various
Acked/Reviewed-by from Kees and Catalin and a note on commit 08/14 suggested
by Kees regarding the removal of STACK_RND_MASK that is safe doing.

I would have appreciated a feedback from a mips maintainer but failed to get
it: can you consider this series for inclusion anyway ? Mips parts have been
reviewed-by Kees.

Thanks,



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 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                 |  11 +++
 fs/binfmt_elf.c                    |  20 ------
 include/linux/mm.h                 |   2 +
 kernel/sysctl.c                    |   6 +-
 mm/util.c                          | 107 ++++++++++++++++++++++++++++-
 17 files changed, 137 insertions(+), 256 deletions(-)

-- 
2.20.1

[PATCH REBASE v4 01/14] mm, fs: Move randomize_stack_top from fs to 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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kees Cook <keescook@chromium.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

[PATCH REBASE v4 02/14] arm64: Make use of is_compat_task instead of hardcoding this test

[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>
---
 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

[PATCH REBASE v4 03/14] arm64: Consider stack randomization for mmap base only when necessary

[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>
---
 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

[PATCH REBASE v4 04/14] arm64, mm: Move generic mmap layout functions to mm

[Alexandre Ghiti]

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>
---
 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 fd5b1a4efc70..7b8d448363f7 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -271,8 +271,6 @@ 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

[PATCH REBASE v4 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout

[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>
---
 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 6a869d9f304f..3f59d0d1632e 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -524,14 +524,6 @@ 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

Re: [PATCH REBASE v4 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout

[Luis Chamberlain]

On Wed, Jul 24, 2019 at 01:58:41AM -0400, Alexandre Ghiti wrote:
> 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;
>  }

So arch_randomize_brk is no longer ifdef'd around
CONFIG_ARCH_HAS_ELF_RANDOMIZE either and yet the header
still has it. Is that intentional?

  Luis

Re: [PATCH REBASE v4 05/14] arm64, mm: Make randomization selected by generic topdown mmap layout

[Alexandre Ghiti]

On 7/24/19 7:11 PM, Luis Chamberlain wrote:
> On Wed, Jul 24, 2019 at 01:58:41AM -0400, Alexandre Ghiti wrote:
>> 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;
>>   }
> So arch_randomize_brk is no longer ifdef'd around
> CONFIG_ARCH_HAS_ELF_RANDOMIZE either and yet the header
> still has it. Is that intentional?
>

Yes, CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects 
CONFIG_ARCH_HAS_ELF_RANDOMIZE, that's what's new about v4: the generic
functions proposed in this series come with elf randomization.


Alex


>    Luis
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH REBASE v4 06/14] arm: Properly account for stack randomization and stack guard gap

[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>
---
 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

[PATCH REBASE v4 07/14] arm: Use STACK_TOP when computing mmap base address

[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>
---
 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

[PATCH REBASE v4 08/14] arm: Use generic mmap top-down layout and brk randomization

[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>
---
 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

[PATCH REBASE v4 09/14] mips: Properly account for stack randomization and stack guard gap

[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>
---
 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

[PATCH REBASE v4 10/14] mips: Use STACK_TOP when computing mmap base address

[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>
---
 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

[PATCH REBASE v4 11/14] mips: Adjust brk randomization offset to fit generic version

[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>
Reviewed-by: Kees Cook <keescook@chromium.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..faa5aa615389 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;
 	else
-		rnd = rnd & 0xffffffful;
+		rnd = rnd & SZ_1G;
 
 	return rnd;
 }
-- 
2.20.1

Re: [PATCH REBASE v4 11/14] mips: Adjust brk randomization offset to fit generic version

[Alexandre Ghiti]

On 7/24/19 7:58 AM, 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>
> Reviewed-by: Kees Cook <keescook@chromium.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..faa5aa615389 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;
>   	else
> -		rnd = rnd & 0xffffffful;
> +		rnd = rnd & SZ_1G;
>   
>   	return rnd;
>   }

Hi Andrew,

I have just noticed that this patch is wrong, do you want me to send
another version of the entire series or is the following diff enough ?
This mistake gets fixed anyway in patch 13/14 when it gets merged with the
generic version.

Sorry about that,

Thanks,

Alex

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;
  }

Re: [PATCH REBASE v4 11/14] mips: Adjust brk randomization offset to fit generic version

[Kees Cook]

On Thu, Jul 25, 2019 at 08:22:06AM +0200, Alexandre Ghiti wrote:
> On 7/24/19 7:58 AM, 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>
> > Reviewed-by: Kees Cook <keescook@chromium.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..faa5aa615389 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;
> >   	else
> > -		rnd = rnd & 0xffffffful;
> > +		rnd = rnd & SZ_1G;
> >   	return rnd;
> >   }
> 
> Hi Andrew,
> 
> I have just noticed that this patch is wrong, do you want me to send
> another version of the entire series or is the following diff enough ?
> This mistake gets fixed anyway in patch 13/14 when it gets merged with the
> generic version.

While I can't speak for Andrew, I'd say, since you've got Paul and
Luis's Acks to add now, I'd say go ahead and respin with the fix and the
Acks added.

I'm really looking forward to this cleanup! Thanks again for working on
it. :)

-- 
Kees Cook

Re: [PATCH REBASE v4 11/14] mips: Adjust brk randomization offset to fit generic version

[Andrew Morton]

On Thu, 25 Jul 2019 13:00:33 -0700 Kees Cook <keescook@chromium.org> wrote:

> > I have just noticed that this patch is wrong, do you want me to send
> > another version of the entire series or is the following diff enough ?
> > This mistake gets fixed anyway in patch 13/14 when it gets merged with the
> > generic version.
> 
> While I can't speak for Andrew, I'd say, since you've got Paul and
> Luis's Acks to add now, I'd say go ahead and respin with the fix and the
> Acks added.

Yes please.   After attending to Paul's questions on [14/14].

[PATCH REBASE v4 12/14] mips: Replace arch specific way to determine 32bit task with generic version

[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>
Reviewed-by: Kees Cook <keescook@chromium.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 faa5aa615389..d4eafbb82789 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;
 	else
 		rnd = rnd & SZ_1G;
-- 
2.20.1

Re: [PATCH REBASE v4 12/14] mips: Replace arch specific way to determine 32bit task with generic version

[Luis Chamberlain]

On Wed, Jul 24, 2019 at 01:58:48AM -0400, Alexandre Ghiti wrote:
> 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>
> Reviewed-by: Kees Cook <keescook@chromium.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 faa5aa615389..d4eafbb82789 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;
>  	else
>  		rnd = rnd & SZ_1G;
> -- 

Since there are at least two users why not just create an inline for
this which describes what we are looking for and remove the comments?

  Luis

Re: [PATCH REBASE v4 12/14] mips: Replace arch specific way to determine 32bit task with generic version

[Alexandre Ghiti]

On 7/24/19 7:16 PM, Luis Chamberlain wrote:
> On Wed, Jul 24, 2019 at 01:58:48AM -0400, Alexandre Ghiti wrote:
>> 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>
>> Reviewed-by: Kees Cook <keescook@chromium.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 faa5aa615389..d4eafbb82789 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;
>>   	else
>>   		rnd = rnd & SZ_1G;
>> -- 
> Since there are at least two users why not just create an inline for
> this which describes what we are looking for and remove the comments?


Actually this is a preparatory patch, this will get merged with the 
generic version in the next patch.

Alex


>
>    Luis
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH REBASE v4 13/14] mips: Use generic mmap top-down layout and brk randomization

[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>
Reviewed-by: Kees Cook <keescook@chromium.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 d4eafbb82789..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;
-	else
-		rnd = rnd & SZ_1G;
-
-	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

[PATCH REBASE v4 14/14] riscv: Make mmap allocation top-down by default

[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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 arch/riscv/Kconfig | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 59a4727ecd6c..6a63973873fd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -54,6 +54,17 @@ 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
+
+# max bits determined by the following formula:
+#  VA_BITS - PAGE_SHIFT - 3
+config ARCH_MMAP_RND_BITS_MAX
+	default 33 if 64BIT # SV48 based
+	default 18
 
 config MMU
 	def_bool y
-- 
2.20.1

Re: [PATCH REBASE v4 14/14] riscv: Make mmap allocation top-down by default

[Paul Walmsley]

Hi Alexandre,

I have a few questions about this patch.  Sorry to be dense here ...

On Wed, 24 Jul 2019, Alexandre Ghiti wrote:

> 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>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/riscv/Kconfig | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 59a4727ecd6c..6a63973873fd 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -54,6 +54,17 @@ 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

Could you help me understand the rationale behind this constant?

> +
> +# max bits determined by the following formula:
> +#  VA_BITS - PAGE_SHIFT - 3

I realize that these lines are probably copied from arch/arm64/Kconfig.  
But the rationale behind the "- 3" is not immediately obvious.  This 
apparently originates from commit 8f0d3aa9de57 ("arm64: mm: support 
ARCH_MMAP_RND_BITS"). Can you provide any additional context here?

> +config ARCH_MMAP_RND_BITS_MAX
> +	default 33 if 64BIT # SV48 based

The rationale here is clear for Sv48, per the above formula:

   (48 - 12 - 3) = 33

> +	default 18

However, here it is less clear to me.  For Sv39, shouldn't this be

   (39 - 12 - 3) = 24

?  And what about Sv32?
 

- Paul

Re: [PATCH REBASE v4 14/14] riscv: Make mmap allocation top-down by default

[Alexandre Ghiti]

On 7/26/19 2:20 AM, Paul Walmsley wrote:
> Hi Alexandre,
>
> I have a few questions about this patch.  Sorry to be dense here ...
>
> On Wed, 24 Jul 2019, Alexandre Ghiti wrote:
>
>> 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>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> ---
>>   arch/riscv/Kconfig | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 59a4727ecd6c..6a63973873fd 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -54,6 +54,17 @@ 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
> Could you help me understand the rationale behind this constant?


Indeed, I took that from arm64 code and I did not think enough about it: 
that's
great you spotted this because that's a way too large value for 32 bits 
as it would,
at minimum, make mmap random offset go up to 1GB (18 + 12), which is a 
big hole for
this small address space :)

arm and mips propose 8 as default value for 32bits systems which is 1MB 
offset at minimum.


>
>> +
>> +# max bits determined by the following formula:
>> +#  VA_BITS - PAGE_SHIFT - 3
> I realize that these lines are probably copied from arch/arm64/Kconfig.
> But the rationale behind the "- 3" is not immediately obvious.  This
> apparently originates from commit 8f0d3aa9de57 ("arm64: mm: support
> ARCH_MMAP_RND_BITS"). Can you provide any additional context here?


The formula comes from commit d07e22597d1d ("mm: mmap: add new /proc tunable
for mmap_base ASLR"), where the author states that "generally a 3-4 bits 
less than the
number of bits in the user-space accessible virtual address space 
[allows to] give the greatest
flexibility without generating an invalid mmap_base address".

In practice, that limits the mmap random offset to at maximum 1/8 (for - 
3) of the total address space.


>
>> +config ARCH_MMAP_RND_BITS_MAX
>> +	default 33 if 64BIT # SV48 based
> The rationale here is clear for Sv48, per the above formula:
>
>     (48 - 12 - 3) = 33
>
>> +	default 18
> However, here it is less clear to me.  For Sv39, shouldn't this be
>
>     (39 - 12 - 3) = 24
>
> ?  And what about Sv32?


You're right. Is there a way to distinguish between sv39 and sv48 here ?

Thanks Paul,

Alex

>   
>
> - Paul
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH REBASE v4 14/14] riscv: Make mmap allocation top-down by default

[Paul Walmsley]

On Fri, 26 Jul 2019, Alexandre Ghiti wrote:

> On 7/26/19 2:20 AM, Paul Walmsley wrote:
> > 
> > On Wed, 24 Jul 2019, Alexandre Ghiti wrote:
> > 
> > > 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>
> > > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > > Reviewed-by: Kees Cook <keescook@chromium.org>
> > > ---
> > >   arch/riscv/Kconfig | 11 +++++++++++
> > >   1 file changed, 11 insertions(+)
> > > 
> > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > > index 59a4727ecd6c..6a63973873fd 100644
> > > --- a/arch/riscv/Kconfig
> > > +++ b/arch/riscv/Kconfig
> > > @@ -54,6 +54,17 @@ 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
> > Could you help me understand the rationale behind this constant?
> 
> 
> Indeed, I took that from arm64 code and I did not think enough about it: 
> that's great you spotted this because that's a way too large value for 
> 32 bits as it would, at minimum, make mmap random offset go up to 1GB 
> (18 + 12), which is a big hole for this small address space :)
> 
> arm and mips propose 8 as default value for 32bits systems which is 1MB offset
> at minimum.

8 seems like a fine minimum for Sv32.

> > > +
> > > +# max bits determined by the following formula:
> > > +#  VA_BITS - PAGE_SHIFT - 3
> > I realize that these lines are probably copied from arch/arm64/Kconfig.
> > But the rationale behind the "- 3" is not immediately obvious.  This
> > apparently originates from commit 8f0d3aa9de57 ("arm64: mm: support
> > ARCH_MMAP_RND_BITS"). Can you provide any additional context here?
> 
> 
> The formula comes from commit d07e22597d1d ("mm: mmap: add new /proc 
> tunable for mmap_base ASLR"), where the author states that "generally a 
> 3-4 bits less than the number of bits in the user-space accessible 
> virtual address space [allows to] give the greatest flexibility without 
> generating an invalid mmap_base address".
> 
> In practice, that limits the mmap random offset to at maximum 1/8 (for - 
> 3) of the total address space.

OK.

> > > +config ARCH_MMAP_RND_BITS_MAX
> > > +	default 33 if 64BIT # SV48 based
> > The rationale here is clear for Sv48, per the above formula:
> > 
> >     (48 - 12 - 3) = 33
> > 
> > > +	default 18
> > However, here it is less clear to me.  For Sv39, shouldn't this be
> > 
> >     (39 - 12 - 3) = 24
> > 
> > ?  And what about Sv32?
> 
> 
> You're right. Is there a way to distinguish between sv39 and sv48 here ?

This patch has just been posted:

https://lore.kernel.org/linux-riscv/alpine.DEB.2.21.9999.1907261259420.26670@viisi.sifive.com/T/#u

Assuming there are no negative comments, we'll plan to send it upstream 
during v5.3-rc.  Your patch should be able to set different minimums and 
maximums based on the value of CONFIG_RISCV_VM_SV*


- Paul

Re: [PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[Luis Chamberlain]

Other than the two comments:

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis

Re: [PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[Alexandre Ghiti]

On 7/24/19 7:17 PM, Luis Chamberlain wrote:
> Other than the two comments:
>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>


Thanks for your time Luis,

Alex


>
>    Luis
>

Re: [EXTERNAL][PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[Paul Burton]

Hi Alexandre,

On Wed, Jul 24, 2019 at 01:58:36AM -0400, Alexandre Ghiti wrote:
> Hi Andrew,
> 
> This is simply a rebase on top of next-20190719, where I added various
> Acked/Reviewed-by from Kees and Catalin and a note on commit 08/14 suggested
> by Kees regarding the removal of STACK_RND_MASK that is safe doing.
> 
> I would have appreciated a feedback from a mips maintainer but failed to get
> it: can you consider this series for inclusion anyway ? Mips parts have been
> reviewed-by Kees.

Whilst skimming email on vacation I hadn't spotted how extensive the
changes in v4 were after acking v3... In any case, for patches 11-13:

    Acked-by: Paul Burton <paul.burton@mips.com>

Thanks,
    Paul

Re: [EXTERNAL][PATCH REBASE v4 00/14] Provide generic top-down mmap layout functions

[Alexandre Ghiti]

On 7/24/19 10:18 PM, Paul Burton wrote:
> Hi Alexandre,
>
> On Wed, Jul 24, 2019 at 01:58:36AM -0400, Alexandre Ghiti wrote:
>> Hi Andrew,
>>
>> This is simply a rebase on top of next-20190719, where I added various
>> Acked/Reviewed-by from Kees and Catalin and a note on commit 08/14 suggested
>> by Kees regarding the removal of STACK_RND_MASK that is safe doing.
>>
>> I would have appreciated a feedback from a mips maintainer but failed to get
>> it: can you consider this series for inclusion anyway ? Mips parts have been
>> reviewed-by Kees.
> Whilst skimming email on vacation I hadn't spotted how extensive the
> changes in v4 were after acking v3... In any case, for patches 11-13:
>
>      Acked-by: Paul Burton <paul.burton@mips.com>


Great, thanks Paul ! I have just noticed there is an error in patch 11/14,
but without much incidence since it gets fixed in patch 13/14. I'll see with
Andrew if he wants a new version or not.


Thanks for your time,


Alex


>
> Thanks,
>      Paul
>