4.9-stable review patch. If anyone has any objections, please let me know.
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From: Ido Schimmel idosch@mellanox.com
[ Upstream commit b4681c2829e24943aadd1a7bb3a30d41d0a20050 ]
Since commit 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse") the local table uses the same trie allocated for the main table when custom rules are not in use.
When a net namespace is dismantled, the main table is flushed and freed (via an RCU callback) before the local table. In case the callback is invoked before the local table is iterated, a use-after-free can occur.
Fix this by iterating over the FIB tables in reverse order, so that the main table is always freed after the local table.
v3: Reworded comment according to Alex's suggestion. v2: Add a comment to make the fix more explicit per Dave's and Alex's feedback.
Fixes: 0ddcf43d5d4a ("ipv4: FIB Local/MAIN table collapse") Signed-off-by: Ido Schimmel idosch@mellanox.com Reported-by: Fengguang Wu fengguang.wu@intel.com Acked-by: Alexander Duyck alexander.h.duyck@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/fib_frontend.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -1253,14 +1253,19 @@ fail:
static void ip_fib_net_exit(struct net *net) { - unsigned int i; + int i;
rtnl_lock(); #ifdef CONFIG_IP_MULTIPLE_TABLES RCU_INIT_POINTER(net->ipv4.fib_main, NULL); RCU_INIT_POINTER(net->ipv4.fib_default, NULL); #endif - for (i = 0; i < FIB_TABLE_HASHSZ; i++) { + /* Destroy the tables in reverse order to guarantee that the + * local table, ID 255, is destroyed before the main table, ID + * 254. This is necessary as the local table may contain + * references to data contained in the main table. + */ + for (i = FIB_TABLE_HASHSZ - 1; i >= 0; i--) { struct hlist_head *head = &net->ipv4.fib_table_hash[i]; struct hlist_node *tmp; struct fib_table *tb;