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    Subject[PATCH 3.16 22/55] net: filter: fix possible use after free
    Date
    3.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Dumazet <edumazet@google.com>

    [ No appicable upstream commit, this bug has been subsequently been
    fixed as a side effect of other changes. ]

    If kmemdup() fails, we free fp->orig_prog and return -ENOMEM

    sk_attach_filter()
    -> sk_filter_uncharge(sk, fp)
    -> sk_filter_release(fp)
    -> call_rcu(&fp->rcu, sk_filter_release_rcu)
    -> sk_filter_release_rcu()
    -> sk_release_orig_filter()
    fprog = fp->orig_prog; // not NULL, but points to freed memory
    kfree(fprog->filter); // use after free, potential corruption
    kfree(fprog); // double free or corruption

    Note: This was fixed in 3.17+ with commit 278571baca2a
    ("net: filter: simplify socket charging")

    Found by AddressSanitizer

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Fixes: a3ea269b8bcdb ("net: filter: keep original BPF program around")
    Acked-by: Alexei Starovoitov <ast@plumgrid.com>
    Acked-by: Daniel Borkmann <dborkman@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/filter.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/core/filter.c
    +++ b/net/core/filter.c
    @@ -1318,6 +1318,7 @@ static int sk_store_orig_filter(struct s
    fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
    if (!fkprog->filter) {
    kfree(fp->orig_prog);
    + fp->orig_prog = NULL;
    return -ENOMEM;
    }




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