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    Subject[PATCH AUTOSEL 4.19 08/38] media: pci: ttpci: av7110: fix possible buffer overflow caused by bad DMA value in debiirq()
    Date
    From: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>

    [ Upstream commit 6499a0db9b0f1e903d52f8244eacc1d4be00eea2 ]

    The value av7110->debi_virt is stored in DMA memory, and it is assigned
    to data, and thus data[0] can be modified at any time by malicious
    hardware. In this case, "if (data[0] < 2)" can be passed, but then
    data[0] can be changed into a large number, which may cause buffer
    overflow when the code "av7110->ci_slot[data[0]]" is used.

    To fix this possible bug, data[0] is assigned to a local variable, which
    replaces the use of data[0].

    Signed-off-by: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>
    Signed-off-by: Sean Young <sean@mess.org>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/media/pci/ttpci/av7110.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/drivers/media/pci/ttpci/av7110.c b/drivers/media/pci/ttpci/av7110.c
    index d6816effb8786..d02b5fd940c12 100644
    --- a/drivers/media/pci/ttpci/av7110.c
    +++ b/drivers/media/pci/ttpci/av7110.c
    @@ -424,14 +424,15 @@ static void debiirq(unsigned long cookie)
    case DATA_CI_GET:
    {
    u8 *data = av7110->debi_virt;
    + u8 data_0 = data[0];

    - if ((data[0] < 2) && data[2] == 0xff) {
    + if (data_0 < 2 && data[2] == 0xff) {
    int flags = 0;
    if (data[5] > 0)
    flags |= CA_CI_MODULE_PRESENT;
    if (data[5] > 5)
    flags |= CA_CI_MODULE_READY;
    - av7110->ci_slot[data[0]].flags = flags;
    + av7110->ci_slot[data_0].flags = flags;
    } else
    ci_get_data(&av7110->ci_rbuffer,
    av7110->debi_virt,
    --
    2.25.1
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