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    Subject[PATCH 4.19 20/56] sch_cake: do not call cake_destroy() from cake_init()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit ab443c53916730862cec202078d36fd4008bea79 ]

    qdiscs are not supposed to call their own destroy() method
    from init(), because core stack already does that.

    syzbot was able to trigger use after free:

    DEBUG_LOCKS_WARN_ON(lock->magic != lock)
    WARNING: CPU: 0 PID: 21902 at kernel/locking/mutex.c:586 __mutex_lock_common kernel/locking/mutex.c:586 [inline]
    WARNING: CPU: 0 PID: 21902 at kernel/locking/mutex.c:586 __mutex_lock+0x9ec/0x12f0 kernel/locking/mutex.c:740
    Modules linked in:
    CPU: 0 PID: 21902 Comm: syz-executor189 Not tainted 5.16.0-rc4-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    RIP: 0010:__mutex_lock_common kernel/locking/mutex.c:586 [inline]
    RIP: 0010:__mutex_lock+0x9ec/0x12f0 kernel/locking/mutex.c:740
    Code: 08 84 d2 0f 85 19 08 00 00 8b 05 97 38 4b 04 85 c0 0f 85 27 f7 ff ff 48 c7 c6 20 00 ac 89 48 c7 c7 a0 fe ab 89 e8 bf 76 ba ff <0f> 0b e9 0d f7 ff ff 48 8b 44 24 40 48 8d b8 c8 08 00 00 48 89 f8
    RSP: 0018:ffffc9000627f290 EFLAGS: 00010282
    RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
    RDX: ffff88802315d700 RSI: ffffffff815f1db8 RDI: fffff52000c4fe44
    RBP: ffff88818f28e000 R08: 0000000000000000 R09: 0000000000000000
    R10: ffffffff815ebb5e R11: 0000000000000000 R12: 0000000000000000
    R13: dffffc0000000000 R14: ffffc9000627f458 R15: 0000000093c30000
    FS: 0000555556abc400(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007fda689c3303 CR3: 000000001cfbb000 CR4: 0000000000350ef0
    Call Trace:
    <TASK>
    tcf_chain0_head_change_cb_del+0x2e/0x3d0 net/sched/cls_api.c:810
    tcf_block_put_ext net/sched/cls_api.c:1381 [inline]
    tcf_block_put_ext net/sched/cls_api.c:1376 [inline]
    tcf_block_put+0xbc/0x130 net/sched/cls_api.c:1394
    cake_destroy+0x3f/0x80 net/sched/sch_cake.c:2695
    qdisc_create.constprop.0+0x9da/0x10f0 net/sched/sch_api.c:1293
    tc_modify_qdisc+0x4c5/0x1980 net/sched/sch_api.c:1660
    rtnetlink_rcv_msg+0x413/0xb80 net/core/rtnetlink.c:5571
    netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2496
    netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
    netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1345
    netlink_sendmsg+0x904/0xdf0 net/netlink/af_netlink.c:1921
    sock_sendmsg_nosec net/socket.c:704 [inline]
    sock_sendmsg+0xcf/0x120 net/socket.c:724
    ____sys_sendmsg+0x6e8/0x810 net/socket.c:2409
    ___sys_sendmsg+0xf3/0x170 net/socket.c:2463
    __sys_sendmsg+0xe5/0x1b0 net/socket.c:2492
    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x7f1bb06badb9
    Code: Unable to access opcode bytes at RIP 0x7f1bb06bad8f.
    RSP: 002b:00007fff3012a658 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
    RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f1bb06badb9
    RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000003
    RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000003
    R10: 0000000000000003 R11: 0000000000000246 R12: 00007fff3012a688
    R13: 00007fff3012a6a0 R14: 00007fff3012a6e0 R15: 00000000000013c2
    </TASK>

    Fixes: 046f6fd5daef ("sched: Add Common Applications Kept Enhanced (cake) qdisc")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
    Link: https://lore.kernel.org/r/20211210142046.698336-1-eric.dumazet@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/sched/sch_cake.c | 6 +-----
    1 file changed, 1 insertion(+), 5 deletions(-)

    diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c
    index 2025f0f559deb..18c207b85d513 100644
    --- a/net/sched/sch_cake.c
    +++ b/net/sched/sch_cake.c
    @@ -2675,7 +2675,7 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
    q->tins = kvcalloc(CAKE_MAX_TINS, sizeof(struct cake_tin_data),
    GFP_KERNEL);
    if (!q->tins)
    - goto nomem;
    + return -ENOMEM;

    for (i = 0; i < CAKE_MAX_TINS; i++) {
    struct cake_tin_data *b = q->tins + i;
    @@ -2705,10 +2705,6 @@ static int cake_init(struct Qdisc *sch, struct nlattr *opt,
    q->min_netlen = ~0;
    q->min_adjlen = ~0;
    return 0;
    -
    -nomem:
    - cake_destroy(sch);
    - return -ENOMEM;
    }

    static int cake_dump(struct Qdisc *sch, struct sk_buff *skb)
    --
    2.33.0


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