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    Subject[PATCH 4.14 41/42] kprobes: dont call disarm_kprobe() for disabled kprobes
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    commit 9c80e79906b4ca440d09e7f116609262bb747909 upstream.

    The assumption in __disable_kprobe() is wrong, and it could try to disarm
    an already disarmed kprobe and fire the WARN_ONCE() below. [0] We can
    easily reproduce this issue.

    1. Write 0 to /sys/kernel/debug/kprobes/enabled.

    # echo 0 > /sys/kernel/debug/kprobes/enabled

    2. Run execsnoop. At this time, one kprobe is disabled.

    # /usr/share/bcc/tools/execsnoop &
    [1] 2460
    PCOMM PID PPID RET ARGS

    # cat /sys/kernel/debug/kprobes/list
    ffffffff91345650 r __x64_sys_execve+0x0 [FTRACE]
    ffffffff91345650 k __x64_sys_execve+0x0 [DISABLED][FTRACE]

    3. Write 1 to /sys/kernel/debug/kprobes/enabled, which changes
    kprobes_all_disarmed to false but does not arm the disabled kprobe.

    # echo 1 > /sys/kernel/debug/kprobes/enabled

    # cat /sys/kernel/debug/kprobes/list
    ffffffff91345650 r __x64_sys_execve+0x0 [FTRACE]
    ffffffff91345650 k __x64_sys_execve+0x0 [DISABLED][FTRACE]

    4. Kill execsnoop, when __disable_kprobe() calls disarm_kprobe() for the
    disabled kprobe and hits the WARN_ONCE() in __disarm_kprobe_ftrace().

    # fg
    /usr/share/bcc/tools/execsnoop
    ^C

    Actually, WARN_ONCE() is fired twice, and __unregister_kprobe_top() misses
    some cleanups and leaves the aggregated kprobe in the hash table. Then,
    __unregister_trace_kprobe() initialises tk->rp.kp.list and creates an
    infinite loop like this.

    aggregated kprobe.list -> kprobe.list -.
    ^ |
    '.__.'

    In this situation, these commands fall into the infinite loop and result
    in RCU stall or soft lockup.

    cat /sys/kernel/debug/kprobes/list : show_kprobe_addr() enters into the
    infinite loop with RCU.

    /usr/share/bcc/tools/execsnoop : warn_kprobe_rereg() holds kprobe_mutex,
    and __get_valid_kprobe() is stuck in
    the loop.

    To avoid the issue, make sure we don't call disarm_kprobe() for disabled
    kprobes.

    [0]
    Failed to disarm kprobe-ftrace at __x64_sys_execve+0x0/0x40 (error -2)
    WARNING: CPU: 6 PID: 2460 at kernel/kprobes.c:1130 __disarm_kprobe_ftrace.isra.19 (kernel/kprobes.c:1129)
    Modules linked in: ena
    CPU: 6 PID: 2460 Comm: execsnoop Not tainted 5.19.0+ #28
    Hardware name: Amazon EC2 c5.2xlarge/, BIOS 1.0 10/16/2017
    RIP: 0010:__disarm_kprobe_ftrace.isra.19 (kernel/kprobes.c:1129)
    Code: 24 8b 02 eb c1 80 3d c4 83 f2 01 00 75 d4 48 8b 75 00 89 c2 48 c7 c7 90 fa 0f 92 89 04 24 c6 05 ab 83 01 e8 e4 94 f0 ff <0f> 0b 8b 04 24 eb b1 89 c6 48 c7 c7 60 fa 0f 92 89 04 24 e8 cc 94
    RSP: 0018:ffff9e6ec154bd98 EFLAGS: 00010282
    RAX: 0000000000000000 RBX: ffffffff930f7b00 RCX: 0000000000000001
    RDX: 0000000080000001 RSI: ffffffff921461c5 RDI: 00000000ffffffff
    RBP: ffff89c504286da8 R08: 0000000000000000 R09: c0000000fffeffff
    R10: 0000000000000000 R11: ffff9e6ec154bc28 R12: ffff89c502394e40
    R13: ffff89c502394c00 R14: ffff9e6ec154bc00 R15: 0000000000000000
    FS: 00007fe800398740(0000) GS:ffff89c812d80000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 000000c00057f010 CR3: 0000000103b54006 CR4: 00000000007706e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    PKRU: 55555554
    Call Trace:
    <TASK>
    __disable_kprobe (kernel/kprobes.c:1716)
    disable_kprobe (kernel/kprobes.c:2392)
    __disable_trace_kprobe (kernel/trace/trace_kprobe.c:340)
    disable_trace_kprobe (kernel/trace/trace_kprobe.c:429)
    perf_trace_event_unreg.isra.2 (./include/linux/tracepoint.h:93 kernel/trace/trace_event_perf.c:168)
    perf_kprobe_destroy (kernel/trace/trace_event_perf.c:295)
    _free_event (kernel/events/core.c:4971)
    perf_event_release_kernel (kernel/events/core.c:5176)
    perf_release (kernel/events/core.c:5186)
    __fput (fs/file_table.c:321)
    task_work_run (./include/linux/sched.h:2056 (discriminator 1) kernel/task_work.c:179 (discriminator 1))
    exit_to_user_mode_prepare (./include/linux/resume_user_mode.h:49 kernel/entry/common.c:169 kernel/entry/common.c:201)
    syscall_exit_to_user_mode (./arch/x86/include/asm/jump_label.h:55 ./arch/x86/include/asm/nospec-branch.h:384 ./arch/x86/include/asm/entry-common.h:94 kernel/entry/common.c:133 kernel/entry/common.c:296)
    do_syscall_64 (arch/x86/entry/common.c:87)
    entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
    RIP: 0033:0x7fe7ff210654
    Code: 15 79 89 20 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb be 0f 1f 00 8b 05 9a cd 20 00 48 63 ff 85 c0 75 11 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3a f3 c3 48 83 ec 18 48 89 7c 24 08 e8 34 fc
    RSP: 002b:00007ffdbd1d3538 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
    RAX: 0000000000000000 RBX: 0000000000000008 RCX: 00007fe7ff210654
    RDX: 0000000000000000 RSI: 0000000000002401 RDI: 0000000000000008
    RBP: 0000000000000000 R08: 94ae31d6fda838a4 R0900007fe8001c9d30
    R10: 00007ffdbd1d34b0 R11: 0000000000000246 R12: 00007ffdbd1d3600
    R13: 0000000000000000 R14: fffffffffffffffc R15: 00007ffdbd1d3560
    </TASK>

    Link: https://lkml.kernel.org/r/20220813020509.90805-1-kuniyu@amazon.com
    Fixes: 69d54b916d83 ("kprobes: makes kprobes/enabled works correctly for optimized kprobes.")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Reported-by: Ayushman Dutta <ayudutta@amazon.com>
    Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
    Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Wang Nan <wangnan0@huawei.com>
    Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
    Cc: Kuniyuki Iwashima <kuni1840@gmail.com>
    Cc: Ayushman Dutta <ayudutta@amazon.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/kprobes.c | 10 ++++++----
    1 file changed, 6 insertions(+), 4 deletions(-)

    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -1687,12 +1687,14 @@ static struct kprobe *__disable_kprobe(s
    /* Try to disarm and disable this/parent probe */
    if (p == orig_p || aggr_kprobe_disabled(orig_p)) {
    /*
    - * If kprobes_all_disarmed is set, orig_p
    - * should have already been disarmed, so
    - * skip unneed disarming process.
    + * Don't be lazy here. Even if 'kprobes_all_disarmed'
    + * is false, 'orig_p' might not have been armed yet.
    + * Note arm_all_kprobes() __tries__ to arm all kprobes
    + * on the best effort basis.
    */
    - if (!kprobes_all_disarmed)
    + if (!kprobes_all_disarmed && !kprobe_disabled(orig_p))
    disarm_kprobe(orig_p, true);
    +
    orig_p->flags |= KPROBE_FLAG_DISABLED;
    }
    }

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