From: Octavian Purdila tavip@google.com
commit b3bf8f63e6179076b57c9de660c9f80b5abefe70 upstream.
It is not sufficient to directly validate the limit on the data that the user passes as it can be updated based on how the other parameters are changed.
Move the check at the end of the configuration update process to also catch scenarios where the limit is indirectly updated, for example with the following configurations:
tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 depth 1 tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 divisor 1
This fixes the following syzkaller reported crash:
------------[ cut here ]------------ UBSAN: array-index-out-of-bounds in net/sched/sch_sfq.c:203:6 index 65535 is out of range for type 'struct sfq_head[128]' CPU: 1 UID: 0 PID: 3037 Comm: syz.2.16 Not tainted 6.14.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x201/0x300 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_out_of_bounds+0xf5/0x120 lib/ubsan.c:429 sfq_link net/sched/sch_sfq.c:203 [inline] sfq_dec+0x53c/0x610 net/sched/sch_sfq.c:231 sfq_dequeue+0x34e/0x8c0 net/sched/sch_sfq.c:493 sfq_reset+0x17/0x60 net/sched/sch_sfq.c:518 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 tbf_reset+0x41/0x110 net/sched/sch_tbf.c:339 qdisc_reset+0x12e/0x600 net/sched/sch_generic.c:1035 dev_reset_queue+0x100/0x1b0 net/sched/sch_generic.c:1311 netdev_for_each_tx_queue include/linux/netdevice.h:2590 [inline] dev_deactivate_many+0x7e5/0xe70 net/sched/sch_generic.c:1375
Reported-by: syzbot syzkaller@googlegroups.com Fixes: 10685681bafc ("net_sched: sch_sfq: don't allow 1 packet limit") Signed-off-by: Octavian Purdila tavip@google.com Acked-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net --- net/sched/sch_sfq.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_sfq.c b/net/sched/sch_sfq.c index 0d916146a5a39b492a89067e19b81628bd72f5d1..04c3aa446ad3d69c014b06e66795b8dfbc369333 100644 --- a/net/sched/sch_sfq.c +++ b/net/sched/sch_sfq.c @@ -658,10 +658,6 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt, if (!p) return -ENOMEM; } - if (ctl->limit == 1) { - NL_SET_ERR_MSG_MOD(extack, "invalid limit"); - return -EINVAL; - }
sch_tree_lock(sch);
@@ -702,6 +698,12 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt, limit = min_t(u32, ctl->limit, maxdepth * maxflows); maxflows = min_t(u32, maxflows, limit); } + if (limit == 1) { + sch_tree_unlock(sch); + kfree(p); + NL_SET_ERR_MSG_MOD(extack, "invalid limit"); + return -EINVAL; + }
/* commit configuration */ q->limit = limit;