media: pci: ttpci: av7110: fix possible buffer overflow caused by bad DMA value in...

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>

diff --git a/drivers/media/pci/ttpci/av7110.c b/drivers/media/pci/ttpci/av7110.c
index d0cdee1c6eb0ba89c1713322e8724760c1235e30..bf36b1e22b6357d8dc639c4e5acb9a0bddca44fd 100644 (file)
--- a/drivers/media/pci/ttpci/av7110.c
+++ b/drivers/media/pci/ttpci/av7110.c
@@ -406,14 +406,15 @@ 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,