The NETLINK_FIB_LOOKUP netlink family can be used to perform a FIB lookup according to user provided parameters and communicate the result back to user space. However, unlike other users of the FIB lookup API, the upper DSCP bits and the ECN bits of the DS field are not masked, which can result in the wrong result being returned. Solve this by masking the upper DSCP bits and the ECN bits using IPTOS_RT_MASK. The structure that communicates the request and the response is not exported to user space, so it is unlikely that this netlink family is actually in use [1]. [1] https://lore.kernel.org/netdev/ZpqpB8vJU%2FQ6LSqa@debian/ Signed-off-by: Ido Schimmel <idosch@xxxxxxxxxx> --- net/ipv4/fib_frontend.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index 7ad2cafb9276..da540ddb7af6 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -1343,7 +1343,7 @@ static void nl_fib_lookup(struct net *net, struct fib_result_nl *frn) struct flowi4 fl4 = { .flowi4_mark = frn->fl_mark, .daddr = frn->fl_addr, - .flowi4_tos = frn->fl_tos, + .flowi4_tos = frn->fl_tos & IPTOS_RT_MASK, .flowi4_scope = frn->fl_scope, }; struct fib_table *tb; -- 2.45.1
