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    SubjectRe: [PATCH] cxgb4: cm: fix a incorrect NULL check on list iterator
    On Sun, 27 Mar 2022 19:38:31 +0300, Leon Romanovsky wrote:
    > On Sun, Mar 27, 2022 at 03:35:42PM +0800, Xiaomeng Tong wrote:
    > > The bug is here:
    > > if (!pdev) {
    > >
    > > The list iterator value 'pdev' will *always* be set and non-NULL
    > > by for_each_netdev(), so it is incorrect to assume that the
    > > iterator value will be NULL if the list is empty or no element
    > > found (in this case, the check 'if (!pdev)' can be bypassed as
    > > it always be false unexpectly).
    > >
    > > To fix the bug, use a new variable 'iter' as the list iterator,
    > > while use the original variable 'pdev' as a dedicated pointer to
    > > point to the found element.
    > I don't think that the description is correct.
    > We are talking about loopback interface which received packet, the pdev will always exist.

    Do the both conditions impossible?
    1. the list is empty or
    2. we can not found a pdev due to this check
    if (ipv6_chk_addr(&init_net,
    (struct in6_addr *)peer_ip,
    pdev, 1))
    iter, 1))

    > Most likely. the check of "if (!pdev)" is to catch impossible situation where IPV6 packet
    > was sent over loopback, but IPV6 is not enabled.

    Xiaomeng Tong

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