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net: fix use after free in xps

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When setting up an new dev_maps in __netif_set_xps_queue, we remove and
free maps from unused CPUs/rx-queues near the end of the function; by
calling remove_xps_queue. However it's possible those maps are also part
of the old not-freed-yet dev_maps, which might be used concurrently.
When that happens, a map can be freed while its corresponding entry in
the old dev_maps table isn't NULLed, leading to: "BUG: KASAN:
use-after-free" in different places.

This fixes the map freeing logic for unused CPUs/rx-queues, to also NULL
the map entries from the old dev_maps table.

Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Antoine Tenart 2021-03-18 19:37:51 +01:00 committed by David S. Miller
parent 2db6cdaeba
commit 2d05bf0153
1 changed files with 12 additions and 5 deletions
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17
net/core/dev.c
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@ -2460,7 +2460,7 @@ static DEFINE_MUTEX(xps_map_mutex);
rcu_dereference_protected((P), lockdep_is_held(&xps_map_mutex))
static bool remove_xps_queue(struct xps_dev_maps *dev_maps,
int tci, u16 index)
struct xps_dev_maps *old_maps, int tci, u16 index)
{
struct xps_map *map = NULL;
int pos;
@ -2479,6 +2479,8 @@ static bool remove_xps_queue(struct xps_dev_maps *dev_maps,
break;
}
if (old_maps)
RCU_INIT_POINTER(old_maps->attr_map[tci], NULL);
RCU_INIT_POINTER(dev_maps->attr_map[tci], NULL);
kfree_rcu(map, rcu);
return false;
@ -2499,7 +2501,7 @@ static bool remove_xps_queue_cpu(struct net_device *dev,
int i, j;
for (i = count, j = offset; i--; j++) {
if (!remove_xps_queue(dev_maps, tci, j))
if (!remove_xps_queue(dev_maps, NULL, tci, j))
break;
}
@ -2631,7 +2633,7 @@ static void xps_copy_dev_maps(struct xps_dev_maps *dev_maps,
int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
u16 index, enum xps_map_type type)
{
struct xps_dev_maps *dev_maps, *new_dev_maps = NULL;
struct xps_dev_maps *dev_maps, *new_dev_maps = NULL, *old_dev_maps = NULL;
const unsigned long *online_mask = NULL;
bool active = false, copy = false;
int i, j, tci, numa_node_id = -2;
@ -2766,7 +2768,7 @@ int __netif_set_xps_queue(struct net_device *dev, const unsigned long *mask,
}
}
kfree_rcu(dev_maps, rcu);
old_dev_maps = dev_maps;
out_no_old_maps:
dev_maps = new_dev_maps;
@ -2792,10 +2794,15 @@ out_no_new_maps:
netif_attr_test_online(j, online_mask, dev_maps->nr_ids))
continue;
active |= remove_xps_queue(dev_maps, tci, index);
active |= remove_xps_queue(dev_maps,
copy ? old_dev_maps : NULL,
tci, index);
}
}
if (old_dev_maps)
kfree_rcu(old_dev_maps, rcu);
/* free map if not active */
if (!active)
reset_xps_maps(dev, dev_maps, type);