Re: [PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 24 Feb 2015 08:39:06 +0100 Ingo Molnar <mingo@kernel.org> wrote:

> 
> * Hector Marco Gisbert <hecmargi@upv.es> wrote:
> 
> > +unsigned long randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + mmap_rnd();
> > +	return (ret > base) ? ret : base;
> > +}
> 
> > +unsigned long randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + mmap_rnd();
> > +	return (ret > base) ? ret : base;
> > +}
> 
> > +unsigned long randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + brk_rnd();
> > +	return (ret > base) ? ret : base;
> > +}
> 
> > +unsigned long randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + mmap_rnd();
> > +	return (ret > base) ? ret : base;
> > +}
> 
> > +unsigned long randomize_et_dyn(unsigned long base)
> > +{
> > +	unsigned long ret;
> > +	if ((current->personality & ADDR_NO_RANDOMIZE) ||
> > +		!(current->flags & PF_RANDOMIZE))
> > +		return base;
> > +	ret = base + mmap_rnd();
> > +	return (ret > base) ? ret : base;
> > +}
> 
> That pointless repetition should be avoided.

That's surprisingly hard!

After renaming mips brk_rnd() to mmap_rnd() I had a shot.  I'm not very
confident in the result.  Does that __weak trick even work?

Someone tell me how important Hector's patch is?


From: Andrew Morton <akpm@linux-foundation.org>
Subject: fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix

Consolidate randomize_et_dyn() implementations into fs/binfmt_elf.c.

There doesn't seem to be a compile-time way of making randomize_et_dyn()
go away on architectures which don't need it, so mark it __weak to cause
it to be discarded at link time.

Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Hector Marco Gisbert <hecmargi@upv.es>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ismael Ripoll <iripoll@upv.es>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/arm/include/asm/elf.h        |    3 +--
 arch/arm/mm/mmap.c                |   13 ++-----------
 arch/arm64/Kconfig                |    2 +-
 arch/arm64/include/asm/elf.h      |    3 +--
 arch/arm64/mm/mmap.c              |   14 ++------------
 arch/mips/include/asm/elf.h       |    1 -
 arch/mips/mm/mmap.c               |   13 ++-----------
 arch/powerpc/include/asm/elf.h    |    2 --
 arch/powerpc/mm/mmap.c            |   13 ++-----------
 arch/x86/include/asm/elf.h        |    2 --
 arch/x86/mm/mmap.c                |   12 ++----------
 fs/binfmt_elf.c                   |   21 +++++++++++++++++++++
 include/linux/elf-randomization.h |    7 +++++++
 13 files changed, 41 insertions(+), 65 deletions(-)

diff -puN arch/arm/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm/Kconfig
diff -puN arch/arm/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm/include/asm/elf.h
--- a/arch/arm/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/arm/include/asm/elf.h
@@ -2,7 +2,7 @@
 #define __ASMARM_ELF_H
 
 #include <asm/hwcap.h>
-
+#include <linux/elf-randomization.h>
 /*
  * ELF register definitions..
  */
@@ -115,7 +115,6 @@ int dump_task_regs(struct task_struct *t
    the loader.  We need to make sure that it is out of the way of the program
    that it will "exec", and that there is sufficient room for the brk.  */
 
-extern unsigned long randomize_et_dyn(unsigned long base);
 #define ELF_ET_DYN_BASE	(randomize_et_dyn(2 * TASK_SIZE / 3))
 
 /* When the program starts, a1 contains a pointer to a function to be 
diff -puN arch/arm/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm/mm/mmap.c
--- a/arch/arm/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/arm/mm/mmap.c
@@ -7,6 +7,7 @@
 #include <linux/shm.h>
 #include <linux/sched.h>
 #include <linux/io.h>
+#include <linux/elf-randomization.h>
 #include <linux/personality.h>
 #include <linux/random.h>
 #include <asm/cachetype.h>
@@ -30,7 +31,7 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-static unsigned long mmap_rnd(void)
+unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = 0;
 
@@ -241,13 +242,3 @@ int devmem_is_allowed(unsigned long pfn)
 }
 
 #endif
-
-unsigned long randomize_et_dyn(unsigned long base)
-{
-	unsigned long ret;
-	if ((current->personality & ADDR_NO_RANDOMIZE) ||
-		!(current->flags & PF_RANDOMIZE))
-		return base;
-	ret = base + mmap_rnd();
-	return (ret > base) ? ret : base;
-}
diff -puN arch/arm64/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm64/Kconfig
--- a/arch/arm64/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/arm64/Kconfig
@@ -1,4 +1,4 @@
-config ARM64
+qconfig ARM64
 	def_bool y
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff -puN arch/arm64/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm64/include/asm/elf.h
--- a/arch/arm64/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/arm64/include/asm/elf.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 20q12 ARM Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
@@ -125,7 +125,6 @@ typedef struct user_fpsimd_state elf_fpr
  * the loader.  We need to make sure that it is out of the way of the program
  * that it will "exec", and that there is sufficient room for the brk.
  */
-extern unsigned long randomize_et_dyn(unsigned long base);
 #define ELF_ET_DYN_BASE	(randomize_et_dyn(2 * TASK_SIZE_64 / 3))
 
 /*
diff -puN arch/arm64/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/arm64/mm/mmap.c
--- a/arch/arm64/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/arm64/mm/mmap.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/elf.h>
+#include <linux/elf-randomization.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
@@ -47,7 +48,7 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-static unsigned long mmap_rnd(void)
+unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = 0;
 
@@ -89,17 +90,6 @@ void arch_pick_mmap_layout(struct mm_str
 }
 EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
 
-unsigned long randomize_et_dyn(unsigned long base)
-{
-	unsigned long ret;
-	if ((current->personality & ADDR_NO_RANDOMIZE) ||
-		!(current->flags & PF_RANDOMIZE))
-		return base;
-	ret = base + mmap_rnd();
-	return (ret > base) ? ret : base;
-}
-
-
 /*
  * You really shouldn't be using read() or write() on /dev/mem.  This might go
  * away in the future.
diff -puN arch/mips/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/mips/Kconfig
diff -puN arch/mips/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/mips/include/asm/elf.h
--- a/arch/mips/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/mips/include/asm/elf.h
@@ -402,7 +402,6 @@ extern const char *__elf_platform;
    that it will "exec", and that there is sufficient room for the brk.	*/
 
 #ifndef ELF_ET_DYN_BASE
-extern unsigned long randomize_et_dyn(unsigned long base);
 #define ELF_ET_DYN_BASE		(randomize_et_dyn(TASK_SIZE / 3 * 2))
 #endif
 
diff -puN arch/mips/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/mips/mm/mmap.c
--- a/arch/mips/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/mips/mm/mmap.c
@@ -9,6 +9,7 @@
 #include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
+#include <linux/elf-randomization.h>
 #include <linux/mman.h>
 #include <linux/module.h>
 #include <linux/personality.h>
@@ -164,7 +165,7 @@ void arch_pick_mmap_layout(struct mm_str
 	}
 }
 
-static inline unsigned long mmap_rnd(void)
+unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = get_random_int();
 
@@ -196,13 +197,3 @@ int __virt_addr_valid(const volatile voi
 	return pfn_valid(PFN_DOWN(virt_to_phys(kaddr)));
 }
 EXPORT_SYMBOL_GPL(__virt_addr_valid);
-
-unsigned long randomize_et_dyn(unsigned long base)
-{
-	unsigned long ret;
-	if ((current->personality & ADDR_NO_RANDOMIZE) ||
-		!(current->flags & PF_RANDOMIZE))
-		return base;
-	ret = base + brk_rnd();
-	return (ret > base) ? ret : base;
-}
diff -puN arch/powerpc/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/powerpc/Kconfig
diff -puN arch/powerpc/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/powerpc/include/asm/elf.h
--- a/arch/powerpc/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/powerpc/include/asm/elf.h
@@ -27,8 +27,6 @@
    use of this is to invoke "./ld.so someprog" to test out a new version of
    the loader.  We need to make sure that it is out of the way of the program
    that it will "exec", and that there is sufficient room for the brk.  */
-
-extern unsigned long randomize_et_dyn(unsigned long base);
 #define ELF_ET_DYN_BASE	(randomize_et_dyn(0x20000000))
 
 #define ELF_CORE_EFLAGS (is_elf2_task() ? 2 : 0)
diff -puN arch/powerpc/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/powerpc/mm/mmap.c
--- a/arch/powerpc/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/powerpc/mm/mmap.c
@@ -24,6 +24,7 @@
 
 #include <linux/personality.h>
 #include <linux/mm.h>
+#include <linux/elf-randomization.h>
 #include <linux/random.h>
 #include <linux/sched.h>
 
@@ -53,7 +54,7 @@ static inline int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-static unsigned long mmap_rnd(void)
+unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = 0;
 
@@ -97,13 +98,3 @@ void arch_pick_mmap_layout(struct mm_str
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 	}
 }
-
-unsigned long randomize_et_dyn(unsigned long base)
-{
-	unsigned long ret;
-	if ((current->personality & ADDR_NO_RANDOMIZE) ||
-		!(current->flags & PF_RANDOMIZE))
-		return base;
-	ret = base + mmap_rnd();
-	return (ret > base) ? ret : base;
-}
diff -puN arch/x86/Kconfig~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/x86/Kconfig
diff -puN arch/x86/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/x86/include/asm/elf.h
--- a/arch/x86/include/asm/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/x86/include/asm/elf.h
@@ -248,8 +248,6 @@ extern int force_personality32;
    use of this is to invoke "./ld.so someprog" to test out a new version of
    the loader.  We need to make sure that it is out of the way of the program
    that it will "exec", and that there is sufficient room for the brk.  */
-
-extern unsigned long randomize_et_dyn(unsigned long base);
 #define ELF_ET_DYN_BASE		(randomize_et_dyn(TASK_SIZE / 3 * 2))
 
 /* This yields a mask that user programs can use to figure out what
diff -puN arch/x86/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix arch/x86/mm/mmap.c
--- a/arch/x86/mm/mmap.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/arch/x86/mm/mmap.c
@@ -29,6 +29,7 @@
 #include <linux/random.h>
 #include <linux/limits.h>
 #include <linux/sched.h>
+#include <linux/elf-randomization.h>
 #include <asm/elf.h>
 
 struct va_alignment __read_mostly va_align = {
@@ -65,7 +66,7 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-static unsigned long mmap_rnd(void)
+unsigned long mmap_rnd(void)
 {
 	unsigned long rnd = 0;
 
@@ -122,12 +123,3 @@ void arch_pick_mmap_layout(struct mm_str
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 	}
 }
-unsigned long randomize_et_dyn(unsigned long base)
-{
-	unsigned long ret;
-	if ((current->personality & ADDR_NO_RANDOMIZE) ||
-		!(current->flags & PF_RANDOMIZE))
-		return base;
-	ret = base + mmap_rnd();
-	return (ret > base) ? ret : base;
-}
diff -puN fs/Kconfig.binfmt~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix fs/Kconfig.binfmt
diff -puN fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix fs/binfmt_elf.c
--- a/fs/binfmt_elf.c~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix
+++ a/fs/binfmt_elf.c
@@ -22,6 +22,7 @@
 #include <linux/slab.h>
 #include <linux/personality.h>
 #include <linux/elfcore.h>
+#include <linux/elf-randomization.h>
 #include <linux/init.h>
 #include <linux/highuid.h>
 #include <linux/compiler.h>
@@ -2300,6 +2301,26 @@ out:
 
 #endif		/* CONFIG_ELF_CORE */
 
+/* Not all architectures implement mmap_rnd() */
+unsigned long __weak mmap_rnd(void)
+{
+}
+
+/*
+ * Not all architectures use randomize_et_dyn(), so use __weak to let the
+ * linker omit it from vmlinux
+ */
+unsigned long __weak randomize_et_dyn(unsigned long base)
+{
+	unsigned long ret;
+
+	if ((current->personality & ADDR_NO_RANDOMIZE) ||
+		!(current->flags & PF_RANDOMIZE))
+		return base;
+	ret = base + mmap_rnd();
+	return max(ret, base);
+}
+
 static int __init init_elf_binfmt(void)
 {
 	register_binfmt(&elf_format);
diff -puN include/linux/elf.h~fix-offset2lib-issue-for-x86-arm-powerpc-and-mips-fix include/linux/elf.h
diff -puN /dev/null include/linux/elf-randomization.h
--- /dev/null
+++ a/include/linux/elf-randomization.h
@@ -0,0 +1,7 @@
+#ifndef __ELF_RANDOMIZATION_H
+#define __ELF_RANDOMIZATION_H
+
+unsigned long randomize_et_dyn(unsigned long base);
+unsigned long mmap_rnd(void);
+
+#endif	/* __ELF_RANDOMIZATION_H */
_