linux: security patch for CVE-2014-0196

linux/CVE-2014-0196.patch

@@ -0,0 +1,80 @@
+From 4291086b1f081b869c6d79e5b7441633dc3ace00 Mon Sep 17 00:00:00 2001
+From: Peter Hurley <peter@hurleysoftware.com>
+Date: Sat, 3 May 2014 14:04:59 +0200
+Subject: n_tty: Fix n_tty_write crash when echoing in raw mode
+
+The tty atomic_write_lock does not provide an exclusion guarantee for
+the tty driver if the termios settings are LECHO & !OPOST.  And since
+it is unexpected and not allowed to call TTY buffer helpers like
+tty_insert_flip_string concurrently, this may lead to crashes when
+concurrect writers call pty_write. In that case the following two
+writers:
+* the ECHOing from a workqueue and
+* pty_write from the process
+race and can overflow the corresponding TTY buffer like follows.
+
+If we look into tty_insert_flip_string_fixed_flag, there is:
+  int space = __tty_buffer_request_room(port, goal, flags);
+  struct tty_buffer *tb = port->buf.tail;
+  ...
+  memcpy(char_buf_ptr(tb, tb->used), chars, space);
+  ...
+  tb->used += space;
+
+so the race of the two can result in something like this:
+              A                                B
+__tty_buffer_request_room
+                                  __tty_buffer_request_room
+memcpy(buf(tb->used), ...)
+tb->used += space;
+                                  memcpy(buf(tb->used), ...) ->BOOM
+
+B's memcpy is past the tty_buffer due to the previous A's tb->used
+increment.
+
+Since the N_TTY line discipline input processing can output
+concurrently with a tty write, obtain the N_TTY ldisc output_lock to
+serialize echo output with normal tty writes.  This ensures the tty
+buffer helper tty_insert_flip_string is not called concurrently and
+everything is fine.
+
+Note that this is nicely reproducible by an ordinary user using
+forkpty and some setup around that (raw termios + ECHO). And it is
+present in kernels at least after commit
+d945cb9cce20ac7143c2de8d88b187f62db99bdc (pty: Rework the pty layer to
+use the normal buffering logic) in 2.6.31-rc3.
+
+js: add more info to the commit log
+js: switch to bool
+js: lock unconditionally
+js: lock only the tty->ops->write call
+
+References: CVE-2014-0196
+Reported-and-tested-by: Jiri Slaby <jslaby@suse.cz>
+Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
+Signed-off-by: Jiri Slaby <jslaby@suse.cz>
+Cc: Linus Torvalds <torvalds@linux-foundation.org>
+Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
+index 41fe8a0..fe9d129 100644
+--- a/drivers/tty/n_tty.c
++++ b/drivers/tty/n_tty.c
+@@ -2353,8 +2353,12 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
+ 			if (tty->ops->flush_chars)
+ 				tty->ops->flush_chars(tty);
+ 		} else {
++			struct n_tty_data *ldata = tty->disc_data;
++
+ 			while (nr > 0) {
++				mutex_lock(&ldata->output_lock);
+ 				c = tty->ops->write(tty, b, nr);
++				mutex_unlock(&ldata->output_lock);
+ 				if (c < 0) {
+ 					retval = c;
+ 					goto break_out;
+-- 
+cgit v0.10.1
+

linux/PKGBUILD

@@ -8,7 +8,7 @@ pkgname=('linux' 'linux-headers' 'linux-docs')
 _kernelname=${pkgname#linux}
 _basekernel="3.12.15"
 pkgver=3.12.15
-pkgrel=1
+pkgrel=2
 arch=('x86_64')
 url="http://www.kernel.org/"
 license=('GPL2')
@@ -26,6 +26,8 @@ source=("http://www.kernel.org/pub/linux/kernel/v3.x/linux-${_basekernel}.tar.xz
         'aufs3-loopback.patch'
         'aufs3.patch'
         'config.aufs'
+        # cve patches (for tty issue, see patch)
+        CVE-2014-0196.patch
         # standard config files for mkinitcpio ramdisk
         'linux.preset'
         'change-default-console-loglevel.patch')
@@ -80,6 +82,9 @@ prepare() {
 
   cat "${srcdir}/config.aufs" >> ./.config
 
+  # CVE patch
+  patch -p1 -i ${srcdir}/CVE-2014-0196.patch
+
   if [ "${_kernelname}" != "" ]; then
     sed -i "s|CONFIG_LOCALVERSION=.*|CONFIG_LOCALVERSION=\"${_kernelname}\"|g" ./.config
     sed -i "s|CONFIG_LOCALVERSION_AUTO=.*|CONFIG_LOCALVERSION_AUTO=n|" ./.config
@@ -328,3 +333,16 @@ package_linux-docs() {
   # remove a file already in linux package
   rm -f "${pkgdir}/usr/src/linux-${_kernver}/Documentation/DocBook/Makefile"
 }
+sha256sums=('f6116819985f0402392580704bf4b3b2f0dd6d0ab7f16b36a078c5788b17c423'
+            '6fa9dfea3d3bb41464652f07fd036886336be3fbb73e2c06baabd1005af1d2cf'
+            '316d7b429cac1d0b407eb3a36403ecc55813fd3941f517c58ab6514433a7ddd9'
+            'e9604c6d87ae87830c154c1b12065eb6361e503006025497741f15dbaa9fd3ff'
+            '03ec8d29245b222c21aee0a043ab9a48702d252d8460d44541fa9ea65bcea7ce'
+            '68426d50a9e774526d039be3e48cdff8f85ee8a37a77bd1aa0671885a09060ec'
+            '6c9a05787a392bd86da8f0fb66abd32a72808576aa7c635e5c2ae678134b59dd'
+            '86bf44ad0ea7c2afa4b195f8858f07eb8e35562c73290a8ba0ca723ee2a1932e'
+            'c4bc9e482581b2e58bb69a11e42636b5b75f0fa5bf0eb20a034594ec8f40f2d6'
+            'b1b1cf291bd68270b700eb21f19f7b052116d07dde492761227cd94bb775910c'
+            '00c522829c322004ea87ae3e228ebb73aa4b4160068078f8b46a7033490df21f'
+            'f0d90e756f14533ee67afda280500511a62465b4f76adcc5effa95a40045179c'
+            'faced4eb4c47c4eb1a9ee8a5bf8a7c4b49d6b4d78efbe426e410730e6267d182')