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    Subject[PATCH 5.10 49/83] net/sched: sch_taprio: properly cancel timer from taprio_destroy()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit a56d447f196fa9973c568f54c0d76d5391c3b0c0 ]

    There is a comment in qdisc_create() about us not calling ops->reset()
    in some cases.

    err_out4:
    /*
    * Any broken qdiscs that would require a ops->reset() here?
    * The qdisc was never in action so it shouldn't be necessary.
    */

    As taprio sets a timer before actually receiving a packet, we need
    to cancel it from ops->destroy, just in case ops->reset has not
    been called.

    syzbot reported:

    ODEBUG: free active (active state 0) object type: hrtimer hint: advance_sched+0x0/0x9a0 arch/x86/include/asm/atomic64_64.h:22
    WARNING: CPU: 0 PID: 8441 at lib/debugobjects.c:505 debug_print_object+0x16e/0x250 lib/debugobjects.c:505
    Modules linked in:
    CPU: 0 PID: 8441 Comm: syz-executor813 Not tainted 5.14.0-rc6-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:505
    Code: ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 af 00 00 00 48 8b 14 dd e0 d3 e3 89 4c 89 ee 48 c7 c7 e0 c7 e3 89 e8 5b 86 11 05 <0f> 0b 83 05 85 03 92 09 01 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e c3
    RSP: 0018:ffffc9000130f330 EFLAGS: 00010282
    RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
    RDX: ffff88802baeb880 RSI: ffffffff815d87b5 RDI: fffff52000261e58
    RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
    R10: ffffffff815d25ee R11: 0000000000000000 R12: ffffffff898dd020
    R13: ffffffff89e3ce20 R14: ffffffff81653630 R15: dffffc0000000000
    FS: 0000000000f0d300(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007ffb64b3e000 CR3: 0000000036557000 CR4: 00000000001506e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    __debug_check_no_obj_freed lib/debugobjects.c:987 [inline]
    debug_check_no_obj_freed+0x301/0x420 lib/debugobjects.c:1018
    slab_free_hook mm/slub.c:1603 [inline]
    slab_free_freelist_hook+0x171/0x240 mm/slub.c:1653
    slab_free mm/slub.c:3213 [inline]
    kfree+0xe4/0x540 mm/slub.c:4267
    qdisc_create+0xbcf/0x1320 net/sched/sch_api.c:1299
    tc_modify_qdisc+0x4c8/0x1a60 net/sched/sch_api.c:1663
    rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5571
    netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2504
    netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
    netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1340
    netlink_sendmsg+0x86d/0xdb0 net/netlink/af_netlink.c:1929
    sock_sendmsg_nosec net/socket.c:704 [inline]
    sock_sendmsg+0xcf/0x120 net/socket.c:724
    ____sys_sendmsg+0x6e8/0x810 net/socket.c:2403
    ___sys_sendmsg+0xf3/0x170 net/socket.c:2457
    __sys_sendmsg+0xe5/0x1b0 net/socket.c:2486
    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80

    Fixes: 44d4775ca518 ("net/sched: sch_taprio: reset child qdiscs before freeing them")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Davide Caratti <dcaratti@redhat.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
    Acked-by: Davide Caratti <dcaratti@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/sched/sch_taprio.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
    index cb5e5220da55..93899559ba6d 100644
    --- a/net/sched/sch_taprio.c
    +++ b/net/sched/sch_taprio.c
    @@ -1630,6 +1630,10 @@ static void taprio_destroy(struct Qdisc *sch)
    list_del(&q->taprio_list);
    spin_unlock(&taprio_list_lock);

    + /* Note that taprio_reset() might not be called if an error
    + * happens in qdisc_create(), after taprio_init() has been called.
    + */
    + hrtimer_cancel(&q->advance_timer);

    taprio_disable_offload(dev, q, NULL);

    --
    2.33.0


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