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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Dave Taht , linux-kernel@vger.kernel.org (open list) Subject: [PATCH net v8 6/6] net/sched: netem: check for negative latency and jitter Date: Fri, 17 Apr 2026 20:19:44 -0700 Message-ID: <20260418032027.900913-7-stephen@networkplumber.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260418032027.900913-1-stephen@networkplumber.org> References: <20260418032027.900913-1-stephen@networkplumber.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Reject requests with negative latency or jitter. A negative value added to current timestamp (u64) wraps to an enormous time_to_send, disabling dequeue. The original UAPI used u32 for these values; the conversion to 64-bit time values via TCA_NETEM_LATENCY64 and TCA_NETEM_JITTER64 allowed signed values to reach the kernel without validation. Jitter is already silently clamped by an abs() in netem_change(); that abs() can be removed in a follow-up once this rejection is in place. Fixes: 99803171ef04 ("netem: add uapi to express delay and jitter in nanoseconds") Signed-off-by: Stephen Hemminger --- net/sched/sch_netem.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 475c14b3dbdb..bc18e1976b6e 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -826,6 +826,16 @@ static int get_dist_table(struct disttable **tbl, const struct nlattr *attr) return 0; } +static int validate_time(const struct nlattr *attr, const char *name, + struct netlink_ext_ack *extack) +{ + if (nla_get_s64(attr) < 0) { + NL_SET_ERR_MSG_ATTR_FMT(extack, attr, "negative %s", name); + return -EINVAL; + } + return 0; +} + static int validate_slot(const struct nlattr *attr, struct netlink_ext_ack *extack) { const struct tc_netem_slot *c = nla_data(attr); @@ -1068,6 +1078,18 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt, goto table_free; } + if (tb[TCA_NETEM_LATENCY64]) { + ret = validate_time(tb[TCA_NETEM_LATENCY64], "latency", extack); + if (ret) + goto table_free; + } + + if (tb[TCA_NETEM_JITTER64]) { + ret = validate_time(tb[TCA_NETEM_JITTER64], "jitter", extack); + if (ret) + goto table_free; + } + sch_tree_lock(sch); /* backup q->clg and q->loss_model */ old_clg = q->clg; -- 2.53.0