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    Subject[PATCH 4.9 20/65] netfilter: nf_tables: Align nft_expr private data to 64-bit
    Date
    From: Lukas Wunner <lukas@wunner.de>

    commit 250367c59e6ba0d79d702a059712d66edacd4a1a upstream.

    Invoking the following commands on a 32-bit architecture with strict
    alignment requirements (such as an ARMv7-based Raspberry Pi) results
    in an alignment exception:

    # nft add table ip test-ip4
    # nft add chain ip test-ip4 output { type filter hook output priority 0; }
    # nft add rule ip test-ip4 output quota 1025 bytes

    Alignment trap: not handling instruction e1b26f9f at [<7f4473f8>]
    Unhandled fault: alignment exception (0x001) at 0xb832e824
    Internal error: : 1 [#1] PREEMPT SMP ARM
    Hardware name: BCM2835
    [<7f4473fc>] (nft_quota_do_init [nft_quota])
    [<7f447448>] (nft_quota_init [nft_quota])
    [<7f4260d0>] (nf_tables_newrule [nf_tables])
    [<7f4168dc>] (nfnetlink_rcv_batch [nfnetlink])
    [<7f416bd0>] (nfnetlink_rcv [nfnetlink])
    [<8078b334>] (netlink_unicast)
    [<8078b664>] (netlink_sendmsg)
    [<8071b47c>] (sock_sendmsg)
    [<8071bd18>] (___sys_sendmsg)
    [<8071ce3c>] (__sys_sendmsg)
    [<8071ce94>] (sys_sendmsg)

    The reason is that nft_quota_do_init() calls atomic64_set() on an
    atomic64_t which is only aligned to 32-bit, not 64-bit, because it
    succeeds struct nft_expr in memory which only contains a 32-bit pointer.
    Fix by aligning the nft_expr private data to 64-bit.

    Fixes: 96518518cc41 ("netfilter: add nftables")
    Signed-off-by: Lukas Wunner <lukas@wunner.de>
    Cc: stable@vger.kernel.org # v3.13+
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    include/net/netfilter/nf_tables.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/include/net/netfilter/nf_tables.h
    +++ b/include/net/netfilter/nf_tables.h
    @@ -705,7 +705,8 @@ struct nft_expr_ops {
    */
    struct nft_expr {
    const struct nft_expr_ops *ops;
    - unsigned char data[];
    + unsigned char data[]
    + __attribute__((aligned(__alignof__(u64))));
    };

    static inline void *nft_expr_priv(const struct nft_expr *expr)

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