[PATCH 5.10 13/22] net: prevent user from passing illegal stab size

Greg Kroah-Hartman
2021-10-14T15:02:16Z

From: 王贇 <yun.wang@linux.alibaba.com>

[ Upstream commit b193e15ac69d56f35e1d8e2b5d16cbd47764d053 ]

We observed below report when playing with netlink sock:

UBSAN: shift-out-of-bounds in net/sched/sch_api.c:580:10
shift exponent 249 is too large for 32-bit type
CPU: 0 PID: 685 Comm: a.out Not tainted
Call Trace:
dump_stack_lvl+0x8d/0xcf
ubsan_epilogue+0xa/0x4e
__ubsan_handle_shift_out_of_bounds+0x161/0x182
__qdisc_calculate_pkt_len+0xf0/0x190
__dev_queue_xmit+0x2ed/0x15b0

it seems like kernel won't check the stab log value passing from
user, and will use the insane value later to calculate pkt_len.

This patch just add a check on the size/cell_log to avoid insane
calculation.

Reported-by: Abaci <abaci@linux.alibaba.com>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/pkt_sched.h | 1 +
net/sched/sch_api.c | 6 ++++++
2 files changed, 7 insertions(+)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 2be90a54a404..7e58b4470570 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -11,6 +11,7 @@
#include <uapi/linux/pkt_sched.h>

#define DEFAULT_TX_QUEUE_LEN 1000
+#define STAB_SIZE_LOG_MAX 30

struct qdisc_walker {
int stop;
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 54a8c363bcdd..7b24582a8a16 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -513,6 +513,12 @@ static struct qdisc_size_table *qdisc_get_stab(struct nlattr *opt,
return stab;
}

+ if (s->size_log > STAB_SIZE_LOG_MAX ||
+ s->cell_log > STAB_SIZE_LOG_MAX) {
+ NL_SET_ERR_MSG(extack, "Invalid logarithmic size of size table");
+ return ERR_PTR(-EINVAL);
+ }
+
stab = kmalloc(sizeof(*stab) + tsize * sizeof(u16), GFP_KERNEL);
if (!stab)
return ERR_PTR(-ENOMEM);
--
2.33.0