[kernel/f20] CVE-2015-1593 stack ASLR integer overflow (rhbz 1192519 1192520)
Josh Boyer
jwboyer at fedoraproject.org
Mon Feb 16 19:19:30 UTC 2015
commit b36b25c6857765d76ef01df6714b55289944e0b9
Author: Josh Boyer <jwboyer at fedoraproject.org>
Date: Mon Feb 16 14:13:37 2015 -0500
CVE-2015-1593 stack ASLR integer overflow (rhbz 1192519 1192520)
...fix-stack-randomization-on-64-bit-systems.patch | 104 ++++++++++++++++++++
kernel.spec | 9 ++
2 files changed, 113 insertions(+), 0 deletions(-)
---
diff --git a/ASLR-fix-stack-randomization-on-64-bit-systems.patch b/ASLR-fix-stack-randomization-on-64-bit-systems.patch
new file mode 100644
index 0000000..077059a
--- /dev/null
+++ b/ASLR-fix-stack-randomization-on-64-bit-systems.patch
@@ -0,0 +1,104 @@
+From: Hector Marco-Gisbert <hecmargi at 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 at upv.es>
+Signed-off-by: Ismael Ripoll <iripoll at upv.es>
+[kees: rebase, fix 80 char, clean up commit message, add test example, cve]
+Signed-off-by: Kees Cook <keescook at chromium.org>
+Cc: stable at 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 d8fc0605b9d2..e1efcaa1b245 100644
+--- a/fs/binfmt_elf.c
++++ b/fs/binfmt_elf.c
+@@ -554,11 +554,12 @@ 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
+
diff --git a/kernel.spec b/kernel.spec
index 3eb06d7..6c25d92 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -758,6 +758,9 @@ Patch30003: 0001-ntp-Fixup-adjtimex-freq-validation-on-32bit-systems.patch
#rhbz 1186097
Patch30004: acpi-video-add-disable_native_backlight_quirk_for_samsung_510r.patch
+#CVE-2015-1593 rhbz 1192519 1192520
+Patch26135: ASLR-fix-stack-randomization-on-64-bit-systems.patch
+
# END OF PATCH DEFINITIONS
%endif
@@ -1479,6 +1482,9 @@ ApplyPatch 0001-ntp-Fixup-adjtimex-freq-validation-on-32bit-systems.patch
#rhbz 1186097
ApplyPatch acpi-video-add-disable_native_backlight_quirk_for_samsung_510r.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.
@@ -2297,6 +2303,9 @@ fi
# ||----w |
# || ||
%changelog
+* Mon Feb 16 2015 Josh Boyer <jwboyer at fedoraproject.org>
+- CVE-2015-1593 stack ASLR integer overflow (rhbz 1192519 1192520)
+
* Wed Feb 11 2015 Justin M. Forbes <jforbes at fedoraproject.org> - 3.18.7-100
- Linux v3.18.7
- Add disable_native_backlight quirk for Samsung 510R (rhbz 1186097)
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