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Add netdev all_adj_list refcnt propagation to fix panic
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This is a respin of a patch to fix a relatively easily reproducible kernel
panic related to the all_adj_list handling for netdevs in recent kernels.

The following sequence of commands will reproduce the issue:

ip link add link eth0 name eth0.100 type vlan id 100
ip link add link eth0 name eth0.200 type vlan id 200
ip link add name testbr type bridge
ip link set eth0.100 master testbr
ip link set eth0.200 master testbr
ip link add link testbr mac0 type macvlan
ip link delete dev testbr

This creates an upper/lower tree of (excuse the poor ASCII art):

            /---eth0.100-eth0
mac0-testbr-
            \---eth0.200-eth0

When testbr is deleted, the all_adj_lists are walked, and eth0 is deleted twice from
the mac0 list. Unfortunately, during setup in __netdev_upper_dev_link, only one
reference to eth0 is added, so this results in a panic.

This change adds reference count propagation so things are handled properly.

Matthias Schiffer reported a similar crash in batman-adv:

freifunk-gluon/gluon#680
https://www.open-mesh.org/issues/247

which this patch also seems to resolve.

Signed-off-by: Andrew Collins <acollins@cradlepoint.com>
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apc-cradlepoint authored and 0day robot committed Oct 3, 2016
1 parent 1cceda7 commit b919d2d
Showing 1 changed file with 37 additions and 31 deletions.
68 changes: 37 additions & 31 deletions net/core/dev.c
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Expand Up @@ -5578,6 +5578,7 @@ static inline bool netdev_adjacent_is_neigh_list(struct net_device *dev,

static int __netdev_adjacent_dev_insert(struct net_device *dev,
struct net_device *adj_dev,
u16 ref_nr,
struct list_head *dev_list,
void *private, bool master)
{
Expand All @@ -5587,7 +5588,7 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
adj = __netdev_find_adj(adj_dev, dev_list);

if (adj) {
adj->ref_nr++;
adj->ref_nr += ref_nr;
return 0;
}

Expand All @@ -5597,7 +5598,7 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,

adj->dev = adj_dev;
adj->master = master;
adj->ref_nr = 1;
adj->ref_nr = ref_nr;
adj->private = private;
dev_hold(adj_dev);

Expand Down Expand Up @@ -5636,6 +5637,7 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,

static void __netdev_adjacent_dev_remove(struct net_device *dev,
struct net_device *adj_dev,
u16 ref_nr,
struct list_head *dev_list)
{
struct netdev_adjacent *adj;
Expand All @@ -5648,10 +5650,10 @@ static void __netdev_adjacent_dev_remove(struct net_device *dev,
BUG();
}

if (adj->ref_nr > 1) {
pr_debug("%s to %s ref_nr-- = %d\n", dev->name, adj_dev->name,
adj->ref_nr-1);
adj->ref_nr--;
if (adj->ref_nr > ref_nr) {
pr_debug("%s to %s ref_nr-%d = %d\n", dev->name, adj_dev->name,
ref_nr, adj->ref_nr-ref_nr);
adj->ref_nr -= ref_nr;
return;
}

Expand All @@ -5670,49 +5672,53 @@ static void __netdev_adjacent_dev_remove(struct net_device *dev,

static int __netdev_adjacent_dev_link_lists(struct net_device *dev,
struct net_device *upper_dev,
u16 ref_nr,
struct list_head *up_list,
struct list_head *down_list,
void *private, bool master)
{
int ret;

ret = __netdev_adjacent_dev_insert(dev, upper_dev, up_list, private,
master);
ret = __netdev_adjacent_dev_insert(dev, upper_dev, ref_nr, up_list,
private, master);
if (ret)
return ret;

ret = __netdev_adjacent_dev_insert(upper_dev, dev, down_list, private,
false);
ret = __netdev_adjacent_dev_insert(upper_dev, dev, ref_nr, down_list,
private, false);
if (ret) {
__netdev_adjacent_dev_remove(dev, upper_dev, up_list);
__netdev_adjacent_dev_remove(dev, upper_dev, ref_nr, up_list);
return ret;
}

return 0;
}

static int __netdev_adjacent_dev_link(struct net_device *dev,
struct net_device *upper_dev)
struct net_device *upper_dev,
u16 ref_nr)
{
return __netdev_adjacent_dev_link_lists(dev, upper_dev,
return __netdev_adjacent_dev_link_lists(dev, upper_dev, ref_nr,
&dev->all_adj_list.upper,
&upper_dev->all_adj_list.lower,
NULL, false);
}

static void __netdev_adjacent_dev_unlink_lists(struct net_device *dev,
struct net_device *upper_dev,
u16 ref_nr,
struct list_head *up_list,
struct list_head *down_list)
{
__netdev_adjacent_dev_remove(dev, upper_dev, up_list);
__netdev_adjacent_dev_remove(upper_dev, dev, down_list);
__netdev_adjacent_dev_remove(dev, upper_dev, ref_nr, up_list);
__netdev_adjacent_dev_remove(upper_dev, dev, ref_nr, down_list);
}

static void __netdev_adjacent_dev_unlink(struct net_device *dev,
struct net_device *upper_dev)
struct net_device *upper_dev,
u16 ref_nr)
{
__netdev_adjacent_dev_unlink_lists(dev, upper_dev,
__netdev_adjacent_dev_unlink_lists(dev, upper_dev, ref_nr,
&dev->all_adj_list.upper,
&upper_dev->all_adj_list.lower);
}
Expand All @@ -5721,17 +5727,17 @@ static int __netdev_adjacent_dev_link_neighbour(struct net_device *dev,
struct net_device *upper_dev,
void *private, bool master)
{
int ret = __netdev_adjacent_dev_link(dev, upper_dev);
int ret = __netdev_adjacent_dev_link(dev, upper_dev, 1);

if (ret)
return ret;

ret = __netdev_adjacent_dev_link_lists(dev, upper_dev,
ret = __netdev_adjacent_dev_link_lists(dev, upper_dev, 1,
&dev->adj_list.upper,
&upper_dev->adj_list.lower,
private, master);
if (ret) {
__netdev_adjacent_dev_unlink(dev, upper_dev);
__netdev_adjacent_dev_unlink(dev, upper_dev, 1);
return ret;
}

Expand All @@ -5741,8 +5747,8 @@ static int __netdev_adjacent_dev_link_neighbour(struct net_device *dev,
static void __netdev_adjacent_dev_unlink_neighbour(struct net_device *dev,
struct net_device *upper_dev)
{
__netdev_adjacent_dev_unlink(dev, upper_dev);
__netdev_adjacent_dev_unlink_lists(dev, upper_dev,
__netdev_adjacent_dev_unlink(dev, upper_dev, 1);
__netdev_adjacent_dev_unlink_lists(dev, upper_dev, 1,
&dev->adj_list.upper,
&upper_dev->adj_list.lower);
}
Expand Down Expand Up @@ -5795,7 +5801,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(j, &upper_dev->all_adj_list.upper, list) {
pr_debug("Interlinking %s with %s, non-neighbour\n",
i->dev->name, j->dev->name);
ret = __netdev_adjacent_dev_link(i->dev, j->dev);
ret = __netdev_adjacent_dev_link(i->dev, j->dev, i->ref_nr);
if (ret)
goto rollback_mesh;
}
Expand All @@ -5805,7 +5811,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(i, &upper_dev->all_adj_list.upper, list) {
pr_debug("linking %s's upper device %s with %s\n",
upper_dev->name, i->dev->name, dev->name);
ret = __netdev_adjacent_dev_link(dev, i->dev);
ret = __netdev_adjacent_dev_link(dev, i->dev, i->ref_nr);
if (ret)
goto rollback_upper_mesh;
}
Expand All @@ -5814,7 +5820,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(i, &dev->all_adj_list.lower, list) {
pr_debug("linking %s's lower device %s with %s\n", dev->name,
i->dev->name, upper_dev->name);
ret = __netdev_adjacent_dev_link(i->dev, upper_dev);
ret = __netdev_adjacent_dev_link(i->dev, upper_dev, i->ref_nr);
if (ret)
goto rollback_lower_mesh;
}
Expand All @@ -5832,7 +5838,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(i, &dev->all_adj_list.lower, list) {
if (i == to_i)
break;
__netdev_adjacent_dev_unlink(i->dev, upper_dev);
__netdev_adjacent_dev_unlink(i->dev, upper_dev, i->ref_nr);
}

i = NULL;
Expand All @@ -5842,7 +5848,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(i, &upper_dev->all_adj_list.upper, list) {
if (i == to_i)
break;
__netdev_adjacent_dev_unlink(dev, i->dev);
__netdev_adjacent_dev_unlink(dev, i->dev, i->ref_nr);
}

i = j = NULL;
Expand All @@ -5854,7 +5860,7 @@ static int __netdev_upper_dev_link(struct net_device *dev,
list_for_each_entry(j, &upper_dev->all_adj_list.upper, list) {
if (i == to_i && j == to_j)
break;
__netdev_adjacent_dev_unlink(i->dev, j->dev);
__netdev_adjacent_dev_unlink(i->dev, j->dev, i->ref_nr);
}
if (i == to_i)
break;
Expand Down Expand Up @@ -5934,16 +5940,16 @@ void netdev_upper_dev_unlink(struct net_device *dev,
*/
list_for_each_entry(i, &dev->all_adj_list.lower, list)
list_for_each_entry(j, &upper_dev->all_adj_list.upper, list)
__netdev_adjacent_dev_unlink(i->dev, j->dev);
__netdev_adjacent_dev_unlink(i->dev, j->dev, i->ref_nr);

/* remove also the devices itself from lower/upper device
* list
*/
list_for_each_entry(i, &dev->all_adj_list.lower, list)
__netdev_adjacent_dev_unlink(i->dev, upper_dev);
__netdev_adjacent_dev_unlink(i->dev, upper_dev, i->ref_nr);

list_for_each_entry(i, &upper_dev->all_adj_list.upper, list)
__netdev_adjacent_dev_unlink(dev, i->dev);
__netdev_adjacent_dev_unlink(dev, i->dev, i->ref_nr);

call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
&changeupper_info.info);
Expand Down

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