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

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 000000000..b382815f8
--- /dev/null
+++ b/ASLR-fix-stack-randomization-on-64-bit-systems.patch
@@ -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
+
diff --git a/kernel.spec b/kernel.spec
index b36b1e1ae..78e8c3b91 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -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