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CVE-2015-1593 stack ASLR integer overflow (rhbz 1192519 1192520)

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Josh Boyer 2015-02-16 14:13:37 -05:00
parent 7e89ce359c
commit d2fb0bf021
2 changed files with 113 additions and 0 deletions
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104
ASLR-fix-stack-randomization-on-64-bit-systems.patch Normal file
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@ -0,0 +1,104 @@
From: Hector Marco-Gisbert <hecmargi@upv.es>
Date: Sat, 14 Feb 2015 09:33:50 -0800
Subject: [PATCH] ASLR: fix stack randomization on 64-bit systems
The issue is that the stack for processes is not properly randomized on 64 bit
architectures due to an integer overflow.
The affected function is randomize_stack_top() in file "fs/binfmt_elf.c":
static unsigned long randomize_stack_top(unsigned long stack_top)
{
unsigned int random_variable = 0;
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE)) {
random_variable = get_random_int() & STACK_RND_MASK;
random_variable <<= PAGE_SHIFT;
}
return PAGE_ALIGN(stack_top) + random_variable;
return PAGE_ALIGN(stack_top) - random_variable;
}
Note that, it declares the "random_variable" variable as "unsigned int". Since
the result of the shifting operation between STACK_RND_MASK (which is
0x3fffff on x86_64, 22 bits) and PAGE_SHIFT (which is 12 on x86_64):
random_variable <<= PAGE_SHIFT;
then the two leftmost bits are dropped when storing the result in the
"random_variable". This variable shall be at least 34 bits long to hold the
(22+12) result.
These two dropped bits have an impact on the entropy of process stack.
Concretely, the total stack entropy is reduced by four: from 2^28 to 2^30 (One
fourth of expected entropy).
This patch restores back the entropy by correcting the types involved in the
operations in the functions randomize_stack_top() and stack_maxrandom_size().
The successful fix can be tested with:
$ for i in `seq 1 10`; do cat /proc/self/maps | grep stack; done
7ffeda566000-7ffeda587000 rw-p 00000000 00:00 0 [stack]
7fff5a332000-7fff5a353000 rw-p 00000000 00:00 0 [stack]
7ffcdb7a1000-7ffcdb7c2000 rw-p 00000000 00:00 0 [stack]
7ffd5e2c4000-7ffd5e2e5000 rw-p 00000000 00:00 0 [stack]
...
Once corrected, the leading bytes should be between 7ffc and 7fff, rather
than always being 7fff.
CVE-2015-1593
Signed-off-by: Hector Marco-Gisbert <hecmargi@upv.es>
Signed-off-by: Ismael Ripoll <iripoll@upv.es>
[kees: rebase, fix 80 char, clean up commit message, add test example, cve]
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
---
arch/x86/mm/mmap.c | 6 +++---
fs/binfmt_elf.c | 5 +++--
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index 919b91205cd4..df4552bd239e 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -35,12 +35,12 @@ struct va_alignment __read_mostly va_align = {
.flags = -1,
};
-static unsigned int stack_maxrandom_size(void)
+static unsigned long stack_maxrandom_size(void)
{
- unsigned int max = 0;
+ unsigned long max = 0;
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE)) {
- max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
+ max = ((-1UL) & STACK_RND_MASK) << PAGE_SHIFT;
}
return max;
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 02b16910f4c9..995986b8e36b 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -645,11 +645,12 @@ out:
static unsigned long randomize_stack_top(unsigned long stack_top)
{
- unsigned int random_variable = 0;
+ unsigned long random_variable = 0;
if ((current->flags & PF_RANDOMIZE) &&
!(current->personality & ADDR_NO_RANDOMIZE)) {
- random_variable = get_random_int() & STACK_RND_MASK;
+ random_variable = (unsigned long) get_random_int();
+ random_variable &= STACK_RND_MASK;
random_variable <<= PAGE_SHIFT;
}
#ifdef CONFIG_STACK_GROWSUP
--
2.1.0

9
kernel.spec
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@ -617,6 +617,9 @@ Patch26133: ntp-Fixup-adjtimex-freq-validation-on-32bit-systems.patch
Patch26134: perf-tools-Define-_GNU_SOURCE-on-pthread_attr_setaff.patch
#CVE-2015-1593 rhbz 1192519 1192520
Patch26135: ASLR-fix-stack-randomization-on-64-bit-systems.patch
# git clone ssh://git.fedorahosted.org/git/kernel-arm64.git, git diff master...devel
Patch30000: kernel-arm64.patch
@ -1343,6 +1346,9 @@ ApplyPatch ntp-Fixup-adjtimex-freq-validation-on-32bit-systems.patch
ApplyPatch perf-tools-Define-_GNU_SOURCE-on-pthread_attr_setaff.patch
#CVE-2015-1593 rhbz 1192519 1192520
ApplyPatch ASLR-fix-stack-randomization-on-64-bit-systems.patch
%if 0%{?aarch64patches}
ApplyPatch kernel-arm64.patch
%ifnarch aarch64 # this is stupid, but i want to notice before secondary koji does.
@ -2209,6 +2215,9 @@ fi
# ||----w |
# || ||
%changelog
* Mon Feb 16 2015 Josh Boyer <jwboyer@fedoraproject.org>
- CVE-2015-1593 stack ASLR integer overflow (rhbz 1192519 1192520)
* Mon Feb 16 2015 Peter Robinson <pbrobinson@fedoraproject.org>
- Minor updates for ARMv7/ARM64