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ipv4: provide stronger user input validation in nl_fib_input()

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Alexander reported a KMSAN splat caused by reads of uninitialized
field (tb_id_in) from user provided struct fib_result_nl

It turns out nl_fib_input() sanity tests on user input is a bit
wrong :

User can pretend nlh->nlmsg_len is big enough, but provide
at sendmsg() time a too small buffer.

Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2017-03-21 19:22:28 -07:00 committed by David S. Miller
parent 8c290e60fa
commit c64c0b3cac
1 changed files with 2 additions and 1 deletions
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3
net/ipv4/fib_frontend.c
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@ -1083,7 +1083,8 @@ static void nl_fib_input(struct sk_buff *skb)
net = sock_net(skb->sk);
nlh = nlmsg_hdr(skb);
if (skb->len < NLMSG_HDRLEN || skb->len < nlh->nlmsg_len ||
if (skb->len < nlmsg_total_size(sizeof(*frn)) ||
skb->len < nlh->nlmsg_len ||
nlmsg_len(nlh) < sizeof(*frn))
return;