From: Jamal Hadi Salim jhs@mojatatu.com
commit 02799571714dc5dd6948824b9d080b44a295f695 upstream.
Follows up on: https://lore.kernel.org/all/20220809170518.164662-1-cascardo@canonical.com/
handle of 0 implies from/to of universe realm which is not very sensible.
Lets see what this patch will do: $sudo tc qdisc add dev $DEV root handle 1:0 prio
//lets manufacture a way to insert handle of 0 $sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 \ route to 0 from 0 classid 1:10 action ok
//gets rejected... Error: handle of 0 is not valid. We have an error talking to the kernel, -1
//lets create a legit entry.. sudo tc filter add dev $DEV parent 1:0 protocol ip prio 100 route from 10 \ classid 1:10 action ok
//what did the kernel insert? $sudo tc filter ls dev $DEV parent 1:0 filter protocol ip pref 100 route chain 0 filter protocol ip pref 100 route chain 0 fh 0x000a8000 flowid 1:10 from 10 action order 1: gact action pass random type none pass val 0 index 1 ref 1 bind 1
//Lets try to replace that legit entry with a handle of 0 $ sudo tc filter replace dev $DEV parent 1:0 protocol ip prio 100 \ handle 0x000a8000 route to 0 from 0 classid 1:10 action drop
Error: Replacing with handle of 0 is invalid. We have an error talking to the kernel, -1
And last, lets run Cascardo's POC: $ ./poc 0 0 -22 -22 -22
Signed-off-by: Jamal Hadi Salim jhs@mojatatu.com Acked-by: Stephen Hemminger stephen@networkplumber.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_route.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/net/sched/cls_route.c +++ b/net/sched/cls_route.c @@ -427,6 +427,11 @@ static int route4_set_parms(struct net * return -EINVAL; }
+ if (!nhandle) { + NL_SET_ERR_MSG(extack, "Replacing with handle of 0 is invalid"); + return -EINVAL; + } + h1 = to_hash(nhandle); b = rtnl_dereference(head->table[h1]); if (!b) { @@ -480,6 +485,11 @@ static int route4_change(struct net *net int err; bool new = true;
+ if (!handle) { + NL_SET_ERR_MSG(extack, "Creating with handle of 0 is invalid"); + return -EINVAL; + } + if (opt == NULL) return handle ? -EINVAL : 0;