The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 664b9c4b7392ce723b013201843264bf95481ce5 Mon Sep 17 00:00:00 2001 From: David Ahern dsahern@kernel.org Date: Thu, 30 Dec 2021 17:36:32 -0700 Subject: [PATCH] ipv4: Check attribute length for RTA_FLOW in multipath route

Make sure RTA_FLOW is at least 4B before using.

Fixes: 4e902c57417c ("[IPv4]: FIB configuration using struct fib_config") Signed-off-by: David Ahern dsahern@kernel.org Signed-off-by: David S. Miller davem@davemloft.net

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index f1caa2c1c041..36bc429f1635 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -731,8 +731,13 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh, }

nla = nla_find(attrs, attrlen, RTA_FLOW); - if (nla) + if (nla) { + if (nla_len(nla) < sizeof(u32)) { + NL_SET_ERR_MSG(extack, "Invalid RTA_FLOW"); + return -EINVAL; + } fib_cfg.fc_flow = nla_get_u32(nla); + }

fib_cfg.fc_encap = nla_find(attrs, attrlen, RTA_ENCAP); nla = nla_find(attrs, attrlen, RTA_ENCAP_TYPE); @@ -963,8 +968,14 @@ int fib_nh_match(struct net *net, struct fib_config *cfg, struct fib_info *fi,

#ifdef CONFIG_IP_ROUTE_CLASSID nla = nla_find(attrs, attrlen, RTA_FLOW); - if (nla && nla_get_u32(nla) != nh->nh_tclassid) - return 1; + if (nla) { + if (nla_len(nla) < sizeof(u32)) { + NL_SET_ERR_MSG(extack, "Invalid RTA_FLOW"); + return -EINVAL; + } + if (nla_get_u32(nla) != nh->nh_tclassid) + return 1; + } #endif }