[PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS
Hector Marco Gisbert
hecmargi at upv.es
Tue Feb 24 06:54:36 AEDT 2015
[PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS
The issue appears on PIE linked executables when all memory areas of a
process are randomized. In this case, the attack "offset2lib" de-randomizes
all library areas on 64 bit Linux systems in less than one second.
Further details of the PoC attack at:
http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html
This patch loads the PIE linked executable in a different area than the
libraries. The successful fix can be tested with a simple pie compiled
application:
$ ./show_mmaps_pie
54859ccd6000-54859ccd7000 r-xp ... /tmp/show_mmaps_pie
54859ced6000-54859ced7000 r--p ... /tmp/show_mmaps_pie
54859ced7000-54859ced8000 rw-p ... /tmp/show_mmaps_pie
7f75be764000-7f75be91f000 r-xp ... /lib/x86_64-linux-gnu/libc.so.6
7f75be91f000-7f75beb1f000 ---p ... /lib/x86_64-linux-gnu/libc.so.6
7f75beb1f000-7f75beb23000 r--p ... /lib/x86_64-linux-gnu/libc.so.6
7f75beb23000-7f75beb25000 rw-p ... /lib/x86_64-linux-gnu/libc.so.6
7f75beb25000-7f75beb2a000 rw-p ...
7f75beb2a000-7f75beb4d000 r-xp ... /lib64/ld-linux-x86-64.so.2
7f75bed45000-7f75bed46000 rw-p ...
7f75bed46000-7f75bed47000 r-xp ...
7f75bed47000-7f75bed4c000 rw-p ...
7f75bed4c000-7f75bed4d000 r--p ... /lib64/ld-linux-x86-64.so.2
7f75bed4d000-7f75bed4e000 rw-p ... /lib64/ld-linux-x86-64.so.2
7f75bed4e000-7f75bed4f000 rw-p ...
7fffb3741000-7fffb3762000 rw-p ... [stack]
7fffb377b000-7fffb377d000 r--p ... [vvar]
7fffb377d000-7fffb377f000 r-xp ... [vdso]
Once corrected, the PIE linked application is loaded in a different area.
We updated the "Fixing Offset2lib weakness" page:
http://cybersecurity.upv.es/solutions/aslrv2/aslrv2.html
Signed-off-by: Hector Marco-Gisbert <hecmargi at upv.es>
Signed-off-by: Ismael Ripoll <iripoll at upv.es>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 97d07ed..ee7ea7e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1,7 +1,6 @@
config ARM
bool
default y
- select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAVE_CUSTOM_GPIO_H
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index afb9caf..6755cd8 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -115,7 +115,8 @@ int dump_task_regs(struct task_struct *t,
elf_gregset_t *elfregs);
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. */
-#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3)
+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
registered with atexit, as per the SVR4 ABI. A value of 0 means we
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 5e85ed3..9177100 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -30,6 +30,17 @@ static int mmap_is_legacy(void)
return sysctl_legacy_va_layout;
}
+static unsigned long mmap_rnd(void)
+{
+ unsigned long rnd = 0;
+
+ /* 8 bits of randomness in 20 address space bits */
+ if (current->flags & PF_RANDOMIZE)
+ rnd = (long)get_random_int() % (1 << 8);
+
+ return rnd << PAGE_SHIFT;
+}
+
static unsigned long mmap_base(unsigned long rnd)
{
unsigned long gap = rlimit(RLIMIT_STACK);
@@ -230,3 +241,13 @@ 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 --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1f9a20..5580d90 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1,6 +1,5 @@
config ARM64
def_bool y
- select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_SG_CHAIN
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 1f65be3..01d3aab 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -126,7 +126,7 @@ typedef struct user_fpsimd_state elf_fpregset_t;
* 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 (2 * TASK_SIZE_64 / 3)
+#define ELF_ET_DYN_BASE (randomize_et_dyn(2 * TASK_SIZE_64 / 3))
/*
* When the program starts, a1 contains a pointer to a function to be
@@ -169,7 +169,7 @@ extern unsigned long arch_randomize_brk(struct
mm_struct *mm);
#define COMPAT_ELF_PLATFORM ("v8l")
#endif
-#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3)
+#define COMPAT_ELF_ET_DYN_BASE (randomize_et_dyn(2 * TASK_SIZE_32 / 3))
/* AArch32 registers. */
#define COMPAT_ELF_NGREG 18
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 54922d1..980110c50 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -89,6 +89,16 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
}
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
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 3289969..31cc248 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -23,7 +23,6 @@ config MIPS
select HAVE_KRETPROBES
select HAVE_DEBUG_KMEMLEAK
select HAVE_SYSCALL_TRACEPOINTS
- select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES && 64BIT
select RTC_LIB if !MACH_LOONGSON
select GENERIC_ATOMIC64 if !64BIT
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index eb4d95d..fcac4c99 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -402,7 +402,8 @@ extern const char *__elf_platform;
that it will "exec", and that there is sufficient room for the brk. */
#ifndef ELF_ET_DYN_BASE
-#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2)
+extern unsigned long randomize_et_dyn(unsigned long base);
+#define ELF_ET_DYN_BASE (randomize_et_dyn(TASK_SIZE / 3 * 2))
#endif
#define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index f1baadd..20ad644 100644
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -196,3 +196,13 @@ int __virt_addr_valid(const volatile void *kaddr)
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 --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a2a168e..fa4c877 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -88,7 +88,6 @@ config PPC
select ARCH_MIGHT_HAVE_PC_PARPORT
select ARCH_MIGHT_HAVE_PC_SERIO
select BINFMT_ELF
- select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select OF
select OF_EARLY_FLATTREE
select OF_RESERVED_MEM
diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index 57d289a..4080425 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -28,7 +28,8 @@
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. */
-#define ELF_ET_DYN_BASE 0x20000000
+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 --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index cb8bdbe..3e642e7 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -97,3 +97,13 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
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 --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ba397bd..dcfe16c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -85,7 +85,6 @@ config X86
select HAVE_CMPXCHG_DOUBLE
select HAVE_ARCH_KMEMCHECK
select HAVE_USER_RETURN_NOTIFIER
- select ARCH_BINFMT_ELF_RANDOMIZE_PIE
select HAVE_ARCH_JUMP_LABEL
select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
select SPARSE_IRQ
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index ca3347a..92c6ac4 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -249,7 +249,8 @@ extern int force_personality32;
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. */
-#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2)
+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
instruction set this CPU supports. This could be done in user space,
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 919b912..7b86605 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -122,3 +122,12 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
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 --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index c055d56..1186190 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -27,8 +27,6 @@ config COMPAT_BINFMT_ELF
bool
depends on COMPAT && BINFMT_ELF
-config ARCH_BINFMT_ELF_RANDOMIZE_PIE
- bool
config ARCH_BINFMT_ELF_STATE
bool
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 02b1691..72f7ff5 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -908,21 +908,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
* default mmap base, as well as whatever program they
* might try to exec. This is because the brk will
* follow the loader, and is not movable. */
-#ifdef CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE
- /* Memory randomization might have been switched off
- * in runtime via sysctl or explicit setting of
- * personality flags.
- * If that is the case, retain the original non-zero
- * load_bias value in order to establish proper
- * non-randomized mappings.
- */
- if (current->flags & PF_RANDOMIZE)
- load_bias = 0;
- else
- load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
-#else
load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
-#endif
}
error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,
Kees Cook <keescook at chromium.org> escribió:
> (I've added some additional CCs to make sure the arch maintainers
> notice this patch.)
>
> This patch seems white-space damaged to me. I had to do a lot of
> manual editing to get it to apply. Please use "git format-patch", if
> you're not already. What version of the kernel was this based on?
>
> On Mon, Feb 23, 2015 at 10:37 AM, Hector Marco <hecmargi at upv.es> wrote:
>> [PATCH] Fix offset2lib issue for x86*, ARM*, PowerPC and MIPS
>>
>> The issue appears on PIE linked executables when all memory areas of a
>> process are randomized. In this case, the attack "offset2lib" de-randomizes
>> all library areas on 64 bit Linux systems in less than one second.
>>
>>
>> Further details of the PoC attack at:
>> http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html
>>
>>
>> This patch loads the PIE linked executable in a different area than the
>> libraries. The successful fix can be tested with a simple pie compiled
>> application:
>>
>>
>> $ ./show_mmaps_pie
>> 54859ccd6000-54859ccd7000 r-xp ... /tmp/show_mmaps_pie
>> 54859ced6000-54859ced7000 r--p ... /tmp/show_mmaps_pie
>> 54859ced7000-54859ced8000 rw-p ... /tmp/show_mmaps_pie
>> 7f75be764000-7f75be91f000 r-xp ... /lib/x86_64-linux-gnu/libc.so.6
>> 7f75be91f000-7f75beb1f000 ---p ... /lib/x86_64-linux-gnu/libc.so.6
>> 7f75beb1f000-7f75beb23000 r--p ... /lib/x86_64-linux-gnu/libc.so.6
>> 7f75beb23000-7f75beb25000 rw-p ... /lib/x86_64-linux-gnu/libc.so.6
>> 7f75beb25000-7f75beb2a000 rw-p ...
>> 7f75beb2a000-7f75beb4d000 r-xp ... /lib64/ld-linux-x86-64.so.2
>> 7f75bed45000-7f75bed46000 rw-p ...
>> 7f75bed46000-7f75bed47000 r-xp ...
>> 7f75bed47000-7f75bed4c000 rw-p ...
>> 7f75bed4c000-7f75bed4d000 r--p ... /lib64/ld-linux-x86-64.so.2
>> 7f75bed4d000-7f75bed4e000 rw-p ... /lib64/ld-linux-x86-64.so.2
>> 7f75bed4e000-7f75bed4f000 rw-p ...
>> 7fffb3741000-7fffb3762000 rw-p ... [stack]
>> 7fffb377b000-7fffb377d000 r--p ... [vvar]
>> 7fffb377d000-7fffb377f000 r-xp ... [vdso]
>>
>>
>> Once corrected, the PIE linked application is loaded in a different area.
>
> Thanks for working on this!
>
>>
>> We updated the "Fixing Offset2lib weakness" page:
>> http://cybersecurity.upv.es/solutions/aslrv2/aslrv2.html
>>
>>
>> Signed-off-by: Hector Marco-Gisbert <hecmargi at upv.es>
>> Signed-off-by: Ismael Ripoll <iripoll at upv.es>
>
> Acked-by: Kees Cook <keescook at chromium.org>
>
>>
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index 97d07ed..ee7ea7e 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -1,7 +1,6 @@
>> config ARM
>> bool
>> default y
>> - select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>> select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>> select ARCH_HAVE_CUSTOM_GPIO_H
>> diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
>> index afb9caf..6755cd8 100644
>> --- a/arch/arm/include/asm/elf.h
>> +++ b/arch/arm/include/asm/elf.h
>> @@ -115,7 +115,8 @@ int dump_task_regs(struct task_struct *t, elf_gregset_t
>> *elfregs);
>> 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. */
>>
>> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE / 3)
>> +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
>> registered with atexit, as per the SVR4 ABI. A value of 0 means we
>> diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
>> index 5e85ed3..9177100 100644
>> --- a/arch/arm/mm/mmap.c
>> +++ b/arch/arm/mm/mmap.c
>> @@ -30,6 +30,17 @@ static int mmap_is_legacy(void)
>> return sysctl_legacy_va_layout;
>> }
>>
>> +static unsigned long mmap_rnd(void)
>> +{
>> + unsigned long rnd = 0;
>> +
>> + /* 8 bits of randomness in 20 address space bits */
>> + if (current->flags & PF_RANDOMIZE)
>> + rnd = (long)get_random_int() % (1 << 8);
>> +
>> + return rnd << PAGE_SHIFT;
>> +}
>> +
>> static unsigned long mmap_base(unsigned long rnd)
>> {
>> unsigned long gap = rlimit(RLIMIT_STACK);
>> @@ -230,3 +241,13 @@ 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 --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index b1f9a20..5580d90 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -1,6 +1,5 @@
>> config ARM64
>> def_bool y
>> - select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>> select ARCH_HAS_GCOV_PROFILE_ALL
>> select ARCH_HAS_SG_CHAIN
>> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
>> index 1f65be3..01d3aab 100644
>> --- a/arch/arm64/include/asm/elf.h
>> +++ b/arch/arm64/include/asm/elf.h
>> @@ -126,7 +126,7 @@ typedef struct user_fpsimd_state elf_fpregset_t;
>> * 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 (2 * TASK_SIZE_64 / 3)
>> +#define ELF_ET_DYN_BASE (randomize_et_dyn(2 * TASK_SIZE_64 / 3))
>>
>> /*
>> * When the program starts, a1 contains a pointer to a function to be
>> @@ -169,7 +169,7 @@ extern unsigned long arch_randomize_brk(struct mm_struct
>> *mm);
>> #define COMPAT_ELF_PLATFORM ("v8l")
>> #endif
>>
>> -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3)
>> +#define COMPAT_ELF_ET_DYN_BASE (randomize_et_dyn(2 * TASK_SIZE_32 /
>> 3))
>>
>> /* AArch32 registers. */
>> #define COMPAT_ELF_NGREG 18
>> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
>> index 54922d1..980110c50 100644
>> --- a/arch/arm64/mm/mmap.c
>> +++ b/arch/arm64/mm/mmap.c
>> @@ -89,6 +89,16 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
>> }
>> 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
>> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
>> index 3289969..31cc248 100644
>> --- a/arch/mips/Kconfig
>> +++ b/arch/mips/Kconfig
>> @@ -23,7 +23,6 @@ config MIPS
>> select HAVE_KRETPROBES
>> select HAVE_DEBUG_KMEMLEAK
>> select HAVE_SYSCALL_TRACEPOINTS
>> - select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> select HAVE_ARCH_TRANSPARENT_HUGEPAGE if CPU_SUPPORTS_HUGEPAGES &&
>> 64BIT
>> select RTC_LIB if !MACH_LOONGSON
>> select GENERIC_ATOMIC64 if !64BIT
>> diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
>> index eb4d95d..fcac4c99 100644
>> --- a/arch/mips/include/asm/elf.h
>> +++ b/arch/mips/include/asm/elf.h
>> @@ -402,7 +402,8 @@ extern const char *__elf_platform;
>> that it will "exec", and that there is sufficient room for the brk. */
>>
>> #ifndef ELF_ET_DYN_BASE
>> -#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2)
>> +extern unsigned long randomize_et_dyn(unsigned long base);
>> +#define ELF_ET_DYN_BASE (randomize_et_dyn(TASK_SIZE / 3 *
>> 2))
>> #endif
>>
>> #define ARCH_HAS_SETUP_ADDITIONAL_PAGES 1
>> diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
>> index f1baadd..20ad644 100644
>> --- a/arch/mips/mm/mmap.c
>> +++ b/arch/mips/mm/mmap.c
>> @@ -196,3 +196,13 @@ int __virt_addr_valid(const volatile void *kaddr)
>> 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 --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index a2a168e..fa4c877 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -88,7 +88,6 @@ config PPC
>> select ARCH_MIGHT_HAVE_PC_PARPORT
>> select ARCH_MIGHT_HAVE_PC_SERIO
>> select BINFMT_ELF
>> - select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> select OF
>> select OF_EARLY_FLATTREE
>> select OF_RESERVED_MEM
>> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
>> index 57d289a..4080425 100644
>> --- a/arch/powerpc/include/asm/elf.h
>> +++ b/arch/powerpc/include/asm/elf.h
>> @@ -28,7 +28,8 @@
>> 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. */
>>
>> -#define ELF_ET_DYN_BASE 0x20000000
>> +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 --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
>> index cb8bdbe..3e642e7 100644
>> --- a/arch/powerpc/mm/mmap.c
>> +++ b/arch/powerpc/mm/mmap.c
>> @@ -97,3 +97,13 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
>> 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 --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index ba397bd..dcfe16c 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -85,7 +85,6 @@ config X86
>> select HAVE_CMPXCHG_DOUBLE
>> select HAVE_ARCH_KMEMCHECK
>> select HAVE_USER_RETURN_NOTIFIER
>> - select ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> select HAVE_ARCH_JUMP_LABEL
>> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>> select SPARSE_IRQ
>> diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
>> index ca3347a..92c6ac4 100644
>> --- a/arch/x86/include/asm/elf.h
>> +++ b/arch/x86/include/asm/elf.h
>> @@ -249,7 +249,8 @@ extern int force_personality32;
>> 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. */
>>
>> -#define ELF_ET_DYN_BASE (TASK_SIZE / 3 * 2)
>> +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
>> instruction set this CPU supports. This could be done in user space,
>> diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
>> index 919b912..7b86605 100644
>> --- a/arch/x86/mm/mmap.c
>> +++ b/arch/x86/mm/mmap.c
>> @@ -122,3 +122,12 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
>> 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 --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
>> index c055d56..1186190 100644
>> --- a/fs/Kconfig.binfmt
>> +++ b/fs/Kconfig.binfmt
>> @@ -27,8 +27,6 @@ config COMPAT_BINFMT_ELF
>> bool
>> depends on COMPAT && BINFMT_ELF
>>
>> -config ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> - bool
>>
>> config ARCH_BINFMT_ELF_STATE
>> bool
>> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
>> index 02b1691..72f7ff5 100644
>> --- a/fs/binfmt_elf.c
>> +++ b/fs/binfmt_elf.c
>> @@ -908,21 +908,7 @@ static int load_elf_binary(struct linux_binprm *bprm)
>> * default mmap base, as well as whatever program
>> they
>> * might try to exec. This is because the brk will
>> * follow the loader, and is not movable. */
>> -#ifdef CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE
>> - /* Memory randomization might have been switched off
>> - * in runtime via sysctl or explicit setting of
>> - * personality flags.
>> - * If that is the case, retain the original non-zero
>> - * load_bias value in order to establish proper
>> - * non-randomized mappings.
>> - */
>> - if (current->flags & PF_RANDOMIZE)
>> - load_bias = 0;
>> - else
>> - load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE -
>> vaddr);
>> -#else
>> load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr);
>> -#endif
>> }
>>
>> error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt,
>
> I think this is much cleaner now without
> ARCH_BINFMT_ELF_RANDOMIZE_PIE. I imagine there could be some follow-up
> cleanups to standardize (or at least clearly document) the intended
> levels of entropy in the 4 ASLR regions on each architecture, as it
> currently varies a bit.
>
> Thanks!
>
> -Kees
>
> --
> Kees Cook
> Chrome OS Security
>
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