net/sched: stop qdisc_tree_reduce_backlog on TC_H_ROOT
[ Upstream commit 2e95c4384438adeaa772caa560244b1a2efef816 ]
In qdisc_tree_reduce_backlog, Qdiscs with major handle ffff: are assumed
to be either root or ingress. This assumption is bogus since it's valid
to create egress qdiscs with major handle ffff:
Budimir Markovic found that for qdiscs like DRR that maintain an active
class list, it will cause a UAF with a dangling class pointer.
In 066a3b5b2346, the concern was to avoid iterating over the ingress
qdisc since its parent is itself. The proper fix is to stop when parent
TC_H_ROOT is reached because the only way to retrieve ingress is when a
hierarchy which does not contain a ffff: major handle call into
qdisc_lookup with TC_H_MAJ(TC_H_ROOT).
In the scenario where major ffff: is an egress qdisc in any of the tree
levels, the updates will also propagate to TC_H_ROOT, which then the
iteration must stop.
Fixes: 066a3b5b2346 ("[NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Suggested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
net/sched/sch_api.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Simon Horman <horms@kernel.org>
BUG=b/377213198
TEST=presubmit
RELEASE_NOTE=Fixed KCTF-2e95c43 in the Linux kernel.
cos-patch: security-high
Link: https://patch.msgid.link/20241024165547.418570-1-jhs@mojatatu.com
Change-Id: Ied6348261e0fd510e47443b6ab9ae32827aa0dbd
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/85659
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
1 file changed
