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[4.2.y-ckt,stable] Patch "vfio: Fix bug in vfio_device_get_from_name()" has been added to staging queue

Message ID 1451949735-25577-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Jan. 4, 2016, 11:22 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    vfio: Fix bug in vfio_device_get_from_name()

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From dcc7434f226a0668d8ec9c8459b6b85cb1d7871a Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@suse.de>
Date: Wed, 4 Nov 2015 13:53:26 +0100
Subject: vfio: Fix bug in vfio_device_get_from_name()

commit e324fc82ea453fcbd3898ec7afb792f750c68979 upstream.

The vfio_device_get_from_name() function might return a
non-NULL pointer, when called with a device name that is not
found in the list. This causes undefined behavior, in my
case calling an invalid function pointer later on:

 kernel tried to execute NX-protected page - exploit attempt? (uid: 0)
 BUG: unable to handle kernel paging request at ffff8800cb3ddc08

[...]

 Call Trace:
  [<ffffffffa03bd733>] ? vfio_group_fops_unl_ioctl+0x253/0x410 [vfio]
  [<ffffffff811efc4d>] do_vfs_ioctl+0x2cd/0x4c0
  [<ffffffff811f9657>] ? __fget+0x77/0xb0
  [<ffffffff811efeb9>] SyS_ioctl+0x79/0x90
  [<ffffffff81001bb0>] ? syscall_return_slowpath+0x50/0x130
  [<ffffffff8167f776>] entry_SYSCALL_64_fastpath+0x16/0x75

Fix the issue by returning NULL when there is no device with
the requested name in the list.

Fixes: 4bc94d5dc95d ("vfio: Fix lockdep issue")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/vfio/vfio.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--
1.9.1
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Patch

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 563c510..8c50ea6 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -692,11 +692,12 @@  EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
 static struct vfio_device *vfio_device_get_from_name(struct vfio_group *group,
 						     char *buf)
 {
-	struct vfio_device *device;
+	struct vfio_device *it, *device = NULL;

 	mutex_lock(&group->device_lock);
-	list_for_each_entry(device, &group->device_list, group_next) {
-		if (!strcmp(dev_name(device->dev), buf)) {
+	list_for_each_entry(it, &group->device_list, group_next) {
+		if (!strcmp(dev_name(it->dev), buf)) {
+			device = it;
 			vfio_device_get(device);
 			break;
 		}