From 3c9e9f7320f0138497ef7879c0903246746e0ed3 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Thu, 12 Mar 2015 14:46:23 -0700 Subject: [PATCH] fib_trie: Avoid NULL pointer if local table is not allocated The function fib_unmerge assumed the local table had already been allocated. If that is not the case however when custom rules are applied then this can result in a NULL pointer dereference. In order to prevent this we must check the value of the local table pointer and if it is NULL simply return 0 as there is no local table to separate from the main. Fixes: 0ddcf43d5 ("ipv4: FIB Local/MAIN table collapse") Reported-by: Madhu Challa Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller --- net/ipv4/fib_frontend.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index c1caf9ded280..e5b6b0534c5f 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -156,9 +156,12 @@ int fib_unmerge(struct net *net) { struct fib_table *old, *new; + /* attempt to fetch local table if it has been allocated */ old = fib_get_table(net, RT_TABLE_LOCAL); - new = fib_trie_unmerge(old); + if (!old) + return 0; + new = fib_trie_unmerge(old); if (!new) return -ENOMEM;