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    Subject[Linux-kernel-mentees] [PATCH v2 RESEND] usbhid: Fix slab-out-of-bounds write in hiddev_ioctl_usage()
    Date
    `uref->usage_index` is not always being properly checked, causing
    hiddev_ioctl_usage() to go out of bounds under some cases. Fix it.

    Reported-by: syzbot+34ee1b45d88571c2fa8b@syzkaller.appspotmail.com
    Link: https://syzkaller.appspot.com/bug?id=f2aebe90b8c56806b050a20b36f51ed6acabe802
    Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
    ---
    Change in v2:
    - Add the same check for the `HIDIOCGUSAGE` case. (Suggested by
    Dan Carpenter <dan.carpenter@oracle.com>)

    drivers/hid/usbhid/hiddev.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
    index 4140dea693e9..4f97e6c12059 100644
    --- a/drivers/hid/usbhid/hiddev.c
    +++ b/drivers/hid/usbhid/hiddev.c
    @@ -519,12 +519,16 @@ static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd,

    switch (cmd) {
    case HIDIOCGUSAGE:
    + if (uref->usage_index >= field->report_count)
    + goto inval;
    uref->value = field->value[uref->usage_index];
    if (copy_to_user(user_arg, uref, sizeof(*uref)))
    goto fault;
    goto goodreturn;

    case HIDIOCSUSAGE:
    + if (uref->usage_index >= field->report_count)
    + goto inval;
    field->value[uref->usage_index] = uref->value;
    goto goodreturn;

    --
    2.25.1
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