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    Subject[PATCH 5.10 531/575] net/sched: sch_taprio: fix undefined behavior in ktime_mono_to_any
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 6dc25401cba4d428328eade8ceae717633fdd702 ]

    1) if q->tk_offset == TK_OFFS_MAX, then get_tcp_tstamp() calls
    ktime_mono_to_any() with out-of-bound value.

    2) if q->tk_offset is changed in taprio_parse_clockid(),
    taprio_get_time() might also call ktime_mono_to_any()
    with out-of-bound value as sysbot found:

    UBSAN: array-index-out-of-bounds in kernel/time/timekeeping.c:908:27
    index 3 is out of range for type 'ktime_t *[3]'
    CPU: 1 PID: 25668 Comm: kworker/u4:0 Not tainted 5.15.0-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
    Call Trace:
    <TASK>
    __dump_stack lib/dump_stack.c:88 [inline]
    dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
    ubsan_epilogue+0xb/0x5a lib/ubsan.c:151
    __ubsan_handle_out_of_bounds.cold+0x62/0x6c lib/ubsan.c:291
    ktime_mono_to_any+0x1d4/0x1e0 kernel/time/timekeeping.c:908
    get_tcp_tstamp net/sched/sch_taprio.c:322 [inline]
    get_packet_txtime net/sched/sch_taprio.c:353 [inline]
    taprio_enqueue_one+0x5b0/0x1460 net/sched/sch_taprio.c:420
    taprio_enqueue+0x3b1/0x730 net/sched/sch_taprio.c:485
    dev_qdisc_enqueue+0x40/0x300 net/core/dev.c:3785
    __dev_xmit_skb net/core/dev.c:3869 [inline]
    __dev_queue_xmit+0x1f6e/0x3630 net/core/dev.c:4194
    batadv_send_skb_packet+0x4a9/0x5f0 net/batman-adv/send.c:108
    batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:393 [inline]
    batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:421 [inline]
    batadv_iv_send_outstanding_bat_ogm_packet+0x6d7/0x8e0 net/batman-adv/bat_iv_ogm.c:1701
    process_one_work+0x9b2/0x1690 kernel/workqueue.c:2298
    worker_thread+0x658/0x11f0 kernel/workqueue.c:2445
    kthread+0x405/0x4f0 kernel/kthread.c:327
    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

    Fixes: 7ede7b03484b ("taprio: make clock reference conversions easier")
    Fixes: 54002066100b ("taprio: Adjust timestamps for TCP packets")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Vedang Patel <vedang.patel@intel.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Reviewed-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
    Link: https://lore.kernel.org/r/20211108180815.1822479-1-eric.dumazet@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/sched/sch_taprio.c | 27 +++++++++++++++++----------
    1 file changed, 17 insertions(+), 10 deletions(-)

    diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
    index 93899559ba6d2..806babdd838d2 100644
    --- a/net/sched/sch_taprio.c
    +++ b/net/sched/sch_taprio.c
    @@ -94,18 +94,22 @@ static ktime_t sched_base_time(const struct sched_gate_list *sched)
    return ns_to_ktime(sched->base_time);
    }

    -static ktime_t taprio_get_time(struct taprio_sched *q)
    +static ktime_t taprio_mono_to_any(const struct taprio_sched *q, ktime_t mono)
    {
    - ktime_t mono = ktime_get();
    + /* This pairs with WRITE_ONCE() in taprio_parse_clockid() */
    + enum tk_offsets tk_offset = READ_ONCE(q->tk_offset);

    - switch (q->tk_offset) {
    + switch (tk_offset) {
    case TK_OFFS_MAX:
    return mono;
    default:
    - return ktime_mono_to_any(mono, q->tk_offset);
    + return ktime_mono_to_any(mono, tk_offset);
    }
    +}

    - return KTIME_MAX;
    +static ktime_t taprio_get_time(const struct taprio_sched *q)
    +{
    + return taprio_mono_to_any(q, ktime_get());
    }

    static void taprio_free_sched_cb(struct rcu_head *head)
    @@ -321,7 +325,7 @@ static ktime_t get_tcp_tstamp(struct taprio_sched *q, struct sk_buff *skb)
    return 0;
    }

    - return ktime_mono_to_any(skb->skb_mstamp_ns, q->tk_offset);
    + return taprio_mono_to_any(q, skb->skb_mstamp_ns);
    }

    /* There are a few scenarios where we will have to modify the txtime from
    @@ -1341,6 +1345,7 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb,
    }
    } else if (tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]) {
    int clockid = nla_get_s32(tb[TCA_TAPRIO_ATTR_SCHED_CLOCKID]);
    + enum tk_offsets tk_offset;

    /* We only support static clockids and we don't allow
    * for it to be modified after the first init.
    @@ -1355,22 +1360,24 @@ static int taprio_parse_clockid(struct Qdisc *sch, struct nlattr **tb,

    switch (clockid) {
    case CLOCK_REALTIME:
    - q->tk_offset = TK_OFFS_REAL;
    + tk_offset = TK_OFFS_REAL;
    break;
    case CLOCK_MONOTONIC:
    - q->tk_offset = TK_OFFS_MAX;
    + tk_offset = TK_OFFS_MAX;
    break;
    case CLOCK_BOOTTIME:
    - q->tk_offset = TK_OFFS_BOOT;
    + tk_offset = TK_OFFS_BOOT;
    break;
    case CLOCK_TAI:
    - q->tk_offset = TK_OFFS_TAI;
    + tk_offset = TK_OFFS_TAI;
    break;
    default:
    NL_SET_ERR_MSG(extack, "Invalid 'clockid'");
    err = -EINVAL;
    goto out;
    }
    + /* This pairs with READ_ONCE() in taprio_mono_to_any */
    + WRITE_ONCE(q->tk_offset, tk_offset);

    q->clockid = clockid;
    } else {
    --
    2.33.0


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