diff mbox

[net] ipv4: provide stronger user input validation in nl_fib_input()

Message ID 1490149348.16816.135.camel@edumazet-glaptop3.roam.corp.google.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Eric Dumazet March 22, 2017, 2:22 a.m. UTC 
From: Eric Dumazet <edumazet@google.com>

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>
---
 net/ipv4/fib_frontend.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

David Miller March 22, 2017, 9:18 p.m. UTC | #1 
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 21 Mar 2017 19:22:28 -0700

> From: Eric Dumazet <edumazet@google.com>
> 
> 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>

Applied and queued up for -stable, thanks Eric.
diff mbox

Patch

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 42bfd08109dd78ab509493e8d2205d72845bb3eb..8f2133ffc2ff1b94871408a5f934cb938d3462b5 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -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;