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    Subject[PATCH 5.9 32/49] net: tipc: prevent possible null deref of link
    Date
    From: Cengiz Can <cengiz@kernel.wtf>

    [ Upstream commit 0398ba9e5a4b5675aa571e0445689d3c2e499c2d ]

    `tipc_node_apply_property` does a null check on a `tipc_link_entry`
    pointer but also accesses the same pointer out of the null check block.

    This triggers a warning on Coverity Static Analyzer because we're
    implying that `e->link` can BE null.

    Move "Update MTU for node link entry" line into if block to make sure
    that we're not in a state that `e->link` is null.

    Signed-off-by: Cengiz Can <cengiz@kernel.wtf>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/tipc/node.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    --- a/net/tipc/node.c
    +++ b/net/tipc/node.c
    @@ -2170,9 +2170,11 @@ void tipc_node_apply_property(struct net
    &xmitq);
    else if (prop == TIPC_NLA_PROP_MTU)
    tipc_link_set_mtu(e->link, b->mtu);
    +
    + /* Update MTU for node link entry */
    + e->mtu = tipc_link_mss(e->link);
    }
    - /* Update MTU for node link entry */
    - e->mtu = tipc_link_mss(e->link);
    +
    tipc_node_write_unlock(n);
    tipc_bearer_xmit(net, bearer_id, &xmitq, &e->maddr, NULL);
    }

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