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    Subject[PATCH 5.16 0441/1039] net: mcs7830: handle usb read errors properly
    Date
    From: Pavel Skripkin <paskripkin@gmail.com>

    [ Upstream commit d668769eb9c52b150753f1653f7f5a0aeb8239d2 ]

    Syzbot reported uninit value in mcs7830_bind(). The problem was in
    missing validation check for bytes read via usbnet_read_cmd().

    usbnet_read_cmd() internally calls usb_control_msg(), that returns
    number of bytes read. Code should validate that requested number of bytes
    was actually read.

    So, this patch adds missing size validation check inside
    mcs7830_get_reg() to prevent uninit value bugs

    Reported-and-tested-by: syzbot+003c0a286b9af5412510@syzkaller.appspotmail.com
    Fixes: 2a36d7083438 ("USB: driver for mcs7830 (aka DeLOCK) USB ethernet adapter")
    Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
    Reviewed-by: Arnd Bergmann <arnd@arndb.de>
    Link: https://lore.kernel.org/r/20220106225716.7425-1-paskripkin@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/net/usb/mcs7830.c | 12 ++++++++++--
    1 file changed, 10 insertions(+), 2 deletions(-)

    diff --git a/drivers/net/usb/mcs7830.c b/drivers/net/usb/mcs7830.c
    index 326cc4e749d80..fdda0616704ea 100644
    --- a/drivers/net/usb/mcs7830.c
    +++ b/drivers/net/usb/mcs7830.c
    @@ -108,8 +108,16 @@ static const char driver_name[] = "MOSCHIP usb-ethernet driver";

    static int mcs7830_get_reg(struct usbnet *dev, u16 index, u16 size, void *data)
    {
    - return usbnet_read_cmd(dev, MCS7830_RD_BREQ, MCS7830_RD_BMREQ,
    - 0x0000, index, data, size);
    + int ret;
    +
    + ret = usbnet_read_cmd(dev, MCS7830_RD_BREQ, MCS7830_RD_BMREQ,
    + 0x0000, index, data, size);
    + if (ret < 0)
    + return ret;
    + else if (ret < size)
    + return -ENODATA;
    +
    + return ret;
    }

    static int mcs7830_set_reg(struct usbnet *dev, u16 index, u16 size, const void *data)
    --
    2.34.1


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