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authorChinmay Agarwal <chinagar@codeaurora.org>2021-04-21 22:42:22 +0300
committerDavid S. Miller <davem@davemloft.net>2021-04-22 00:47:43 +0300
commiteefb45eef5c4c425e87667af8f5e904fbdd47abf (patch)
tree57004620aaeb238067499722f84ff3ad733c9025 /net/core
parent83d686a6822322c4981b745dc1d7185f1f40811b (diff)
downloadlinux-eefb45eef5c4c425e87667af8f5e904fbdd47abf.tar.xz
neighbour: Prevent Race condition in neighbour subsytem
Following Race Condition was detected: <CPU A, t0>: Executing: __netif_receive_skb() ->__netif_receive_skb_core() -> arp_rcv() -> arp_process().arp_process() calls __neigh_lookup() which takes a reference on neighbour entry 'n'. Moves further along, arp_process() and calls neigh_update()-> __neigh_update(). Neighbour entry is unlocked just before a call to neigh_update_gc_list. This unlocking paves way for another thread that may take a reference on the same and mark it dead and remove it from gc_list. <CPU B, t1> - neigh_flush_dev() is under execution and calls neigh_mark_dead(n) marking the neighbour entry 'n' as dead. Also n will be removed from gc_list. Moves further along neigh_flush_dev() and calls neigh_cleanup_and_release(n), but since reference count increased in t1, 'n' couldn't be destroyed. <CPU A, t3>- Code hits neigh_update_gc_list, with neighbour entry set as dead. <CPU A, t4> - arp_process() finally calls neigh_release(n), destroying the neighbour entry and we have a destroyed ntry still part of gc_list. Fixes: eb4e8fac00d1("neighbour: Prevent a dead entry from updating gc_list") Signed-off-by: Chinmay Agarwal <chinagar@codeaurora.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/neighbour.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 8379719d1dce..98f20efbfadf 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -131,6 +131,9 @@ static void neigh_update_gc_list(struct neighbour *n)
write_lock_bh(&n->tbl->lock);
write_lock(&n->lock);
+ if (n->dead)
+ goto out;
+
/* remove from the gc list if new state is permanent or if neighbor
* is externally learned; otherwise entry should be on the gc list
*/
@@ -147,6 +150,7 @@ static void neigh_update_gc_list(struct neighbour *n)
atomic_inc(&n->tbl->gc_entries);
}
+out:
write_unlock(&n->lock);
write_unlock_bh(&n->tbl->lock);
}