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    Subject[PATCH 4.19 06/33] net: rose: fix UAF bugs caused by timer handler
    Date
    From: Duoming Zhou <duoming@zju.edu.cn>

    commit 9cc02ede696272c5271a401e4f27c262359bc2f6 upstream.

    There are UAF bugs in rose_heartbeat_expiry(), rose_timer_expiry()
    and rose_idletimer_expiry(). The root cause is that del_timer()
    could not stop the timer handler that is running and the refcount
    of sock is not managed properly.

    One of the UAF bugs is shown below:

    (thread 1) | (thread 2)
    | rose_bind
    | rose_connect
    | rose_start_heartbeat
    rose_release | (wait a time)
    case ROSE_STATE_0 |
    rose_destroy_socket | rose_heartbeat_expiry
    rose_stop_heartbeat |
    sock_put(sk) | ...
    sock_put(sk) // FREE |
    | bh_lock_sock(sk) // USE

    The sock is deallocated by sock_put() in rose_release() and
    then used by bh_lock_sock() in rose_heartbeat_expiry().

    Although rose_destroy_socket() calls rose_stop_heartbeat(),
    it could not stop the timer that is running.

    The KASAN report triggered by POC is shown below:

    BUG: KASAN: use-after-free in _raw_spin_lock+0x5a/0x110
    Write of size 4 at addr ffff88800ae59098 by task swapper/3/0
    ...
    Call Trace:
    <IRQ>
    dump_stack_lvl+0xbf/0xee
    print_address_description+0x7b/0x440
    print_report+0x101/0x230
    ? irq_work_single+0xbb/0x140
    ? _raw_spin_lock+0x5a/0x110
    kasan_report+0xed/0x120
    ? _raw_spin_lock+0x5a/0x110
    kasan_check_range+0x2bd/0x2e0
    _raw_spin_lock+0x5a/0x110
    rose_heartbeat_expiry+0x39/0x370
    ? rose_start_heartbeat+0xb0/0xb0
    call_timer_fn+0x2d/0x1c0
    ? rose_start_heartbeat+0xb0/0xb0
    expire_timers+0x1f3/0x320
    __run_timers+0x3ff/0x4d0
    run_timer_softirq+0x41/0x80
    __do_softirq+0x233/0x544
    irq_exit_rcu+0x41/0xa0
    sysvec_apic_timer_interrupt+0x8c/0xb0
    </IRQ>
    <TASK>
    asm_sysvec_apic_timer_interrupt+0x1b/0x20
    RIP: 0010:default_idle+0xb/0x10
    RSP: 0018:ffffc9000012fea0 EFLAGS: 00000202
    RAX: 000000000000bcae RBX: ffff888006660f00 RCX: 000000000000bcae
    RDX: 0000000000000001 RSI: ffffffff843a11c0 RDI: ffffffff843a1180
    RBP: dffffc0000000000 R08: dffffc0000000000 R09: ffffed100da36d46
    R10: dfffe9100da36d47 R11: ffffffff83cf0950 R12: 0000000000000000
    R13: 1ffff11000ccc1e0 R14: ffffffff8542af28 R15: dffffc0000000000
    ...
    Allocated by task 146:
    __kasan_kmalloc+0xc4/0xf0
    sk_prot_alloc+0xdd/0x1a0
    sk_alloc+0x2d/0x4e0
    rose_create+0x7b/0x330
    __sock_create+0x2dd/0x640
    __sys_socket+0xc7/0x270
    __x64_sys_socket+0x71/0x80
    do_syscall_64+0x43/0x90
    entry_SYSCALL_64_after_hwframe+0x46/0xb0

    Freed by task 152:
    kasan_set_track+0x4c/0x70
    kasan_set_free_info+0x1f/0x40
    ____kasan_slab_free+0x124/0x190
    kfree+0xd3/0x270
    __sk_destruct+0x314/0x460
    rose_release+0x2fa/0x3b0
    sock_close+0xcb/0x230
    __fput+0x2d9/0x650
    task_work_run+0xd6/0x160
    exit_to_user_mode_loop+0xc7/0xd0
    exit_to_user_mode_prepare+0x4e/0x80
    syscall_exit_to_user_mode+0x20/0x40
    do_syscall_64+0x4f/0x90
    entry_SYSCALL_64_after_hwframe+0x46/0xb0

    This patch adds refcount of sock when we use functions
    such as rose_start_heartbeat() and so on to start timer,
    and decreases the refcount of sock when timer is finished
    or deleted by functions such as rose_stop_heartbeat()
    and so on. As a result, the UAF bugs could be mitigated.

    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
    Tested-by: Duoming Zhou <duoming@zju.edu.cn>
    Link: https://lore.kernel.org/r/20220629002640.5693-1-duoming@zju.edu.cn
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/rose/rose_timer.c | 34 +++++++++++++++++++---------------
    1 file changed, 19 insertions(+), 15 deletions(-)

    --- a/net/rose/rose_timer.c
    +++ b/net/rose/rose_timer.c
    @@ -34,89 +34,89 @@ static void rose_idletimer_expiry(struct

    void rose_start_heartbeat(struct sock *sk)
    {
    - del_timer(&sk->sk_timer);
    + sk_stop_timer(sk, &sk->sk_timer);

    sk->sk_timer.function = rose_heartbeat_expiry;
    sk->sk_timer.expires = jiffies + 5 * HZ;

    - add_timer(&sk->sk_timer);
    + sk_reset_timer(sk, &sk->sk_timer, sk->sk_timer.expires);
    }

    void rose_start_t1timer(struct sock *sk)
    {
    struct rose_sock *rose = rose_sk(sk);

    - del_timer(&rose->timer);
    + sk_stop_timer(sk, &rose->timer);

    rose->timer.function = rose_timer_expiry;
    rose->timer.expires = jiffies + rose->t1;

    - add_timer(&rose->timer);
    + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
    }

    void rose_start_t2timer(struct sock *sk)
    {
    struct rose_sock *rose = rose_sk(sk);

    - del_timer(&rose->timer);
    + sk_stop_timer(sk, &rose->timer);

    rose->timer.function = rose_timer_expiry;
    rose->timer.expires = jiffies + rose->t2;

    - add_timer(&rose->timer);
    + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
    }

    void rose_start_t3timer(struct sock *sk)
    {
    struct rose_sock *rose = rose_sk(sk);

    - del_timer(&rose->timer);
    + sk_stop_timer(sk, &rose->timer);

    rose->timer.function = rose_timer_expiry;
    rose->timer.expires = jiffies + rose->t3;

    - add_timer(&rose->timer);
    + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
    }

    void rose_start_hbtimer(struct sock *sk)
    {
    struct rose_sock *rose = rose_sk(sk);

    - del_timer(&rose->timer);
    + sk_stop_timer(sk, &rose->timer);

    rose->timer.function = rose_timer_expiry;
    rose->timer.expires = jiffies + rose->hb;

    - add_timer(&rose->timer);
    + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
    }

    void rose_start_idletimer(struct sock *sk)
    {
    struct rose_sock *rose = rose_sk(sk);

    - del_timer(&rose->idletimer);
    + sk_stop_timer(sk, &rose->idletimer);

    if (rose->idle > 0) {
    rose->idletimer.function = rose_idletimer_expiry;
    rose->idletimer.expires = jiffies + rose->idle;

    - add_timer(&rose->idletimer);
    + sk_reset_timer(sk, &rose->idletimer, rose->idletimer.expires);
    }
    }

    void rose_stop_heartbeat(struct sock *sk)
    {
    - del_timer(&sk->sk_timer);
    + sk_stop_timer(sk, &sk->sk_timer);
    }

    void rose_stop_timer(struct sock *sk)
    {
    - del_timer(&rose_sk(sk)->timer);
    + sk_stop_timer(sk, &rose_sk(sk)->timer);
    }

    void rose_stop_idletimer(struct sock *sk)
    {
    - del_timer(&rose_sk(sk)->idletimer);
    + sk_stop_timer(sk, &rose_sk(sk)->idletimer);
    }

    static void rose_heartbeat_expiry(struct timer_list *t)
    @@ -133,6 +133,7 @@ static void rose_heartbeat_expiry(struct
    (sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_DEAD))) {
    bh_unlock_sock(sk);
    rose_destroy_socket(sk);
    + sock_put(sk);
    return;
    }
    break;
    @@ -155,6 +156,7 @@ static void rose_heartbeat_expiry(struct

    rose_start_heartbeat(sk);
    bh_unlock_sock(sk);
    + sock_put(sk);
    }

    static void rose_timer_expiry(struct timer_list *t)
    @@ -184,6 +186,7 @@ static void rose_timer_expiry(struct tim
    break;
    }
    bh_unlock_sock(sk);
    + sock_put(sk);
    }

    static void rose_idletimer_expiry(struct timer_list *t)
    @@ -208,4 +211,5 @@ static void rose_idletimer_expiry(struct
    sock_set_flag(sk, SOCK_DEAD);
    }
    bh_unlock_sock(sk);
    + sock_put(sk);
    }

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