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    Subject[PATCH 4.16 17/55] net/tls: Dont recursively call push_record during tls_write_space callbacks
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: Dave Watson <davejwatson@fb.com>

    [ Upstream commit c212d2c7fc4736d49be102fb7a1a545cdc2f1fea ]

    It is reported that in some cases, write_space may be called in
    do_tcp_sendpages, such that we recursively invoke do_tcp_sendpages again:

    [ 660.468802] ? do_tcp_sendpages+0x8d/0x580
    [ 660.468826] ? tls_push_sg+0x74/0x130 [tls]
    [ 660.468852] ? tls_push_record+0x24a/0x390 [tls]
    [ 660.468880] ? tls_write_space+0x6a/0x80 [tls]
    ...

    tls_push_sg already does a loop over all sending sg's, so ignore
    any tls_write_space notifications until we are done sending.
    We then have to call the previous write_space to wake up
    poll() waiters after we are done with the send loop.

    Reported-by: Andre Tomt <andre@tomt.net>
    Signed-off-by: Dave Watson <davejwatson@fb.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/net/tls.h | 1 +
    net/tls/tls_main.c | 7 +++++++
    2 files changed, 8 insertions(+)

    --- a/include/net/tls.h
    +++ b/include/net/tls.h
    @@ -102,6 +102,7 @@ struct tls_context {
    struct scatterlist *partially_sent_record;
    u16 partially_sent_offset;
    unsigned long flags;
    + bool in_tcp_sendpages;

    u16 pending_open_record_frags;
    int (*push_pending_record)(struct sock *sk, int flags);
    --- a/net/tls/tls_main.c
    +++ b/net/tls/tls_main.c
    @@ -107,6 +107,7 @@ int tls_push_sg(struct sock *sk,
    size = sg->length - offset;
    offset += sg->offset;

    + ctx->in_tcp_sendpages = true;
    while (1) {
    if (sg_is_last(sg))
    sendpage_flags = flags;
    @@ -141,6 +142,8 @@ retry:
    }

    clear_bit(TLS_PENDING_CLOSED_RECORD, &ctx->flags);
    + ctx->in_tcp_sendpages = false;
    + ctx->sk_write_space(sk);

    return 0;
    }
    @@ -210,6 +213,10 @@ static void tls_write_space(struct sock
    {
    struct tls_context *ctx = tls_get_ctx(sk);

    + /* We are already sending pages, ignore notification */
    + if (ctx->in_tcp_sendpages)
    + return;
    +
    if (!sk->sk_write_pending && tls_is_pending_closed_record(ctx)) {
    gfp_t sk_allocation = sk->sk_allocation;
    int rc;

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