From: Eric Dumazet edumazet@google.com
commit 7d18a07897d07495ee140dd319b0e9265c0f68ba upstream.
tx_queue_len can be set to ~0U, we need to be more careful about overflows.
__fls(0) is undefined, as this report shows:
UBSAN: shift-out-of-bounds in net/sched/sch_qfq.c:1430:24 shift exponent 51770272 is too large for 32-bit type 'int' CPU: 0 PID: 25574 Comm: syz-executor.0 Not tainted 5.16.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x201/0x2d8 lib/dump_stack.c:106 ubsan_epilogue lib/ubsan.c:151 [inline] __ubsan_handle_shift_out_of_bounds+0x494/0x530 lib/ubsan.c:330 qfq_init_qdisc+0x43f/0x450 net/sched/sch_qfq.c:1430 qdisc_create+0x895/0x1430 net/sched/sch_api.c:1253 tc_modify_qdisc+0x9d9/0x1e20 net/sched/sch_api.c:1660 rtnetlink_rcv_msg+0x934/0xe60 net/core/rtnetlink.c:5571 netlink_rcv_skb+0x200/0x470 net/netlink/af_netlink.c:2496 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x814/0x9f0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0xaea/0xe60 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:704 [inline] sock_sendmsg net/socket.c:724 [inline] ____sys_sendmsg+0x5b9/0x910 net/socket.c:2409 ___sys_sendmsg net/socket.c:2463 [inline] __sys_sendmsg+0x280/0x370 net/socket.c:2492 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae
Fixes: 462dbc9101ac ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/sch_qfq.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- a/net/sched/sch_qfq.c +++ b/net/sched/sch_qfq.c @@ -1479,10 +1479,8 @@ static int qfq_init_qdisc(struct Qdisc * if (err < 0) return err;
- if (qdisc_dev(sch)->tx_queue_len + 1 > QFQ_MAX_AGG_CLASSES) - max_classes = QFQ_MAX_AGG_CLASSES; - else - max_classes = qdisc_dev(sch)->tx_queue_len + 1; + max_classes = min_t(u64, (u64)qdisc_dev(sch)->tx_queue_len + 1, + QFQ_MAX_AGG_CLASSES); /* max_cl_shift = floor(log_2(max_classes)) */ max_cl_shift = __fls(max_classes); q->max_agg_classes = 1<<max_cl_shift;