This is a note to let you know that I've just added the patch titled sch_qfq: prevent shift-out-of-bounds in qfq_init_qdisc to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sch_qfq-prevent-shift-out-of-bounds-in-qfq_init_qdisc.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 7d18a07897d07495ee140dd319b0e9265c0f68ba Mon Sep 17 00:00:00 2001 From: Eric Dumazet <edumazet@xxxxxxxxxx> Date: Tue, 4 Jan 2022 01:45:08 -0800 Subject: sch_qfq: prevent shift-out-of-bounds in qfq_init_qdisc From: Eric Dumazet <edumazet@xxxxxxxxxx> 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@xxxxxxxxxx> Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -1430,10 +1430,8 @@ 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; Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are queue-4.19/sch_qfq-prevent-shift-out-of-bounds-in-qfq_init_qdisc.patch