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    Subject[PATCH review for 3.18 19/30] net/packet: check length in getsockopt() called with PACKET_HDRLEN
    Date
    From: Alexander Potapenko <glider@google.com>

    [ Upstream commit fd2c83b35752f0a8236b976978ad4658df14a59f ]

    In the case getsockopt() is called with PACKET_HDRLEN and optlen < 4
    |val| remains uninitialized and the syscall may behave differently
    depending on its value, and even copy garbage to userspace on certain
    architectures. To fix this we now return -EINVAL if optlen is too small.

    This bug has been detected with KMSAN.

    Signed-off-by: Alexander Potapenko <glider@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    ---
    net/packet/af_packet.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
    index 1c03d83edd7e..7effa07c4491 100644
    --- a/net/packet/af_packet.c
    +++ b/net/packet/af_packet.c
    @@ -3482,6 +3482,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
    case PACKET_HDRLEN:
    if (len > sizeof(int))
    len = sizeof(int);
    + if (len < sizeof(int))
    + return -EINVAL;
    if (copy_from_user(&val, optval, len))
    return -EFAULT;
    switch (val) {
    --
    2.11.0
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