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    Subject[PATCH 5.0 009/139] ppp: deflate: Fix possible crash in deflate_init
    Date
    From: YueHaibing <yuehaibing@huawei.com>

    [ Upstream commit 3ebe1bca58c85325c97a22d4fc3f5b5420752e6f ]

    BUG: unable to handle kernel paging request at ffffffffa018f000
    PGD 3270067 P4D 3270067 PUD 3271063 PMD 2307eb067 PTE 0
    Oops: 0000 [#1] PREEMPT SMP
    CPU: 0 PID: 4138 Comm: modprobe Not tainted 5.1.0-rc7+ #1
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
    rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
    RIP: 0010:ppp_register_compressor+0x3e/0xd0 [ppp_generic]
    Code: 98 4a 3f e2 48 8b 15 c1 67 00 00 41 8b 0c 24 48 81 fa 40 f0 19 a0
    75 0e eb 35 48 8b 12 48 81 fa 40 f0 19 a0 74
    RSP: 0018:ffffc90000d93c68 EFLAGS: 00010287
    RAX: ffffffffa018f000 RBX: ffffffffa01a3000 RCX: 000000000000001a
    RDX: ffff888230c750a0 RSI: 0000000000000000 RDI: ffffffffa019f000
    RBP: ffffc90000d93c80 R08: 0000000000000001 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffa0194080
    R13: ffff88822ee1a700 R14: 0000000000000000 R15: ffffc90000d93e78
    FS: 00007f2339557540(0000) GS:ffff888237a00000(0000)
    knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: ffffffffa018f000 CR3: 000000022bde4000 CR4: 00000000000006f0
    Call Trace:
    ? 0xffffffffa01a3000
    deflate_init+0x11/0x1000 [ppp_deflate]
    ? 0xffffffffa01a3000
    do_one_initcall+0x6c/0x3cc
    ? kmem_cache_alloc_trace+0x248/0x3b0
    do_init_module+0x5b/0x1f1
    load_module+0x1db1/0x2690
    ? m_show+0x1d0/0x1d0
    __do_sys_finit_module+0xc5/0xd0
    __x64_sys_finit_module+0x15/0x20
    do_syscall_64+0x6b/0x1d0
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    If ppp_deflate fails to register in deflate_init,
    module initialization failed out, however
    ppp_deflate_draft may has been regiestred and not
    unregistered before return.
    Then the seconed modprobe will trigger crash like this.

    Reported-by: Hulk Robot <hulkci@huawei.com>
    Signed-off-by: YueHaibing <yuehaibing@huawei.com>
    Acked-by: Guillaume Nault <gnault@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/ppp/ppp_deflate.c | 20 ++++++++++++++------
    1 file changed, 14 insertions(+), 6 deletions(-)

    --- a/drivers/net/ppp/ppp_deflate.c
    +++ b/drivers/net/ppp/ppp_deflate.c
    @@ -610,12 +610,20 @@ static struct compressor ppp_deflate_dra

    static int __init deflate_init(void)
    {
    - int answer = ppp_register_compressor(&ppp_deflate);
    - if (answer == 0)
    - printk(KERN_INFO
    - "PPP Deflate Compression module registered\n");
    - ppp_register_compressor(&ppp_deflate_draft);
    - return answer;
    + int rc;
    +
    + rc = ppp_register_compressor(&ppp_deflate);
    + if (rc)
    + return rc;
    +
    + rc = ppp_register_compressor(&ppp_deflate_draft);
    + if (rc) {
    + ppp_unregister_compressor(&ppp_deflate);
    + return rc;
    + }
    +
    + pr_info("PPP Deflate Compression module registered\n");
    + return 0;
    }

    static void __exit deflate_cleanup(void)

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