linux-grsec: XSA-40

2 files changed, 59 insertions, 1 deletions

diff --git a/main/linux-grsec/APKBUILD b/main/linux-grsec/APKBUILD
index 68db9fbb23..f796f5fa81 100644
--- a/main/linux-grsec/APKBUILD
+++ b/main/linux-grsec/APKBUILD
@@ -4,7 +4,7 @@ _flavor=grsec
 pkgname=linux-${_flavor}
 pkgver=3.4.24
 _kernver=3.4
-pkgrel=2
+pkgrel=3
 pkgdesc="Linux kernel with grsecurity"
 url=http://grsecurity.net
 depends="mkinitfs linux-firmware"
@@ -22,6 +22,7 @@ source="http://ftp.kernel.org/pub/linux/kernel/v3.x/linux-$_kernver.tar.xz
 
         0001-r8169-avoid-NAPI-scheduling-delay.patch
         r8169-num-rx-desc.patch
+        xsa40.patch
 
         kernelconfig.x86
         kernelconfig.x86_64
@@ -151,5 +152,6 @@ cb6fcd6e966e73c87a839c4c0183f81f  0001-Revert-ipv4-Don-t-use-the-cached-pmtu-inf
 d2f7ba780ff7567c21381428264d7fdd  intel_idle.patch
 8e5611c6bf3dfb0008d4e58051a8b0ff  0001-r8169-avoid-NAPI-scheduling-delay.patch
 daf2cbb558588c49c138fe9ca2482b64  r8169-num-rx-desc.patch
+d9de28f8a74fe0347866705b4bd6db85  xsa40.patch
 50a13359236dbd676fa355f0b4fd27ff  kernelconfig.x86
 c402f52babc729d1280c1677075aa0d7  kernelconfig.x86_64"
diff --git a/main/linux-grsec/xsa40.patch b/main/linux-grsec/xsa40.patch
new file mode 100644
index 0000000000..29db917cbb
--- /dev/null
+++ b/main/linux-grsec/xsa40.patch
@@ -0,0 +1,56 @@
+Xen: Fix stack corruption in xen_failsafe_callback for 32bit PVOPS guests.
+
+This fixes CVE-2013-0190 / XSA-40
+
+There has been an error on the xen_failsafe_callback path for failed
+iret, which causes the stack pointer to be wrong when entering the
+iret_exc error path.  This can result in the kernel crashing.
+
+In the classic kernel case, the relevant code looked a little like:
+
+        popl %eax      # Error code from hypervisor
+        jz 5f
+        addl $16,%esp
+        jmp iret_exc   # Hypervisor said iret fault
+5:      addl $16,%esp
+                       # Hypervisor said segment selector fault
+
+Here, there are two identical addls on either option of a branch which
+appears to have been optimised by hoisting it above the jz, and
+converting it to an lea, which leaves the flags register unaffected.
+
+In the PVOPS case, the code looks like:
+
+        popl_cfi %eax         # Error from the hypervisor
+        lea 16(%esp),%esp     # Add $16 before choosing fault path
+        CFI_ADJUST_CFA_OFFSET -16
+        jz 5f
+        addl $16,%esp         # Incorrectly adjust %esp again
+        jmp iret_exc
+
+It is possible unprivileged userspace applications to cause this
+behaviour, for example by loading an LDT code selector, then changing
+the code selector to be not-present.  At this point, there is a race
+condition where it is possible for the hypervisor to return back to
+userspace from an interrupt, fault on its own iret, and inject a
+failsafe_callback into the kernel.
+
+This bug has been present since the introduction of Xen PVOPS support
+in commit 5ead97c84 (xen: Core Xen implementation), in 2.6.23.
+
+Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
+Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
+
+diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
+index ff84d54..6ed91d9 100644
+--- a/arch/x86/kernel/entry_32.S
++++ b/arch/x86/kernel/entry_32.S
+@@ -1065,7 +1065,6 @@ ENTRY(xen_failsafe_callback)
+        lea 16(%esp),%esp
+        CFI_ADJUST_CFA_OFFSET -16
+        jz 5f
+-       addl $16,%esp
+        jmp iret_exc
+ 5:     pushl_cfi $-1 /* orig_ax = -1 => not a system call */
+        SAVE_ALL
+