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    SubjectRe: [PATCH 3/3] Compare namespaces when comparing addresses in auth_unix cache.
    Quoting Rob Landley (
    > On 04/08/2011 10:08 AM, Rob Landley wrote:
    > > On 04/04/2011 10:46 PM, Serge E. Hallyn wrote:
    > >> Does this need to take a reference? Or is there no way for an
    > >> entry to outlive its netns? It sort of looks like
    > >> svcauth_unix_info_release will ensure that doesn't happen, but
    > >> I'm not convinced because other parts of the kernel can get
    > >> to ip_map_init through the struct cache_detail.
    > >
    > > When I wrote this I thought the transport's get_net() and put_net()
    > > would pin it, but after re-reading, the sunrpc code is disgustingly
    > > convoluted enough that I can't easily reconstruct my earlier reasoning.
    > > I'll add a get_net() and put_net() just to not have to worry about it.
    > Ah-ha!
    > Stanislav Kinsbursky helped me reconstruct some of the reasoning: we
    > don't need to take a reference because we never actually dereference the
    > struct net *, all we do is feed them to net_eq() which just compares the
    > pointers for equality. (The inline function exists so it can compile to
    > a constant "return 1" when configured out.)
    > So if the network context did go away (which still shouldn't happen
    > between the rpc_xprt and the struct nfs_client having references to it)
    > we still wouldn't have a use-after-free problem because we're not
    > looking at the memory, just the pointer.

    Besides use-after-free, the other concern is an invalid net_eq()
    result due to the * being re-used for a new netns. I assume that's
    deemed "super-duper impossible" again bc of the rpc_xprt/nfs_client
    references to it?

    > So I shouldn't need to add get_net() and put_net() to the cache. Sound
    > about right?


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