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    Subject[PATCH 4.14 30/43] net: remove duplicate fetch in sock_getsockopt
    Date
    From: JingYi Hou <houjingyi647@gmail.com>

    [ Upstream commit d0bae4a0e3d8c5690a885204d7eb2341a5b4884d ]

    In sock_getsockopt(), 'optlen' is fetched the first time from userspace.
    'len < 0' is then checked. Then in condition 'SO_MEMINFO', 'optlen' is
    fetched the second time from userspace.

    If change it between two fetches may cause security problems or unexpected
    behaivor, and there is no reason to fetch it a second time.

    To fix this, we need to remove the second fetch.

    Signed-off-by: JingYi Hou <houjingyi647@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/sock.c | 3 ---
    1 file changed, 3 deletions(-)

    --- a/net/core/sock.c
    +++ b/net/core/sock.c
    @@ -1358,9 +1358,6 @@ int sock_getsockopt(struct socket *sock,
    {
    u32 meminfo[SK_MEMINFO_VARS];

    - if (get_user(len, optlen))
    - return -EFAULT;
    -
    sk_get_meminfo(sk, meminfo);

    len = min_t(unsigned int, len, sizeof(meminfo));

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