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Message-ID: <9f8f7a96-fcb0-3088-6d2f-d7e7d0fc83a1@linux.alibaba.com> Date: Thu, 12 Oct 2023 10:49:30 +0800 From: "D. Wythe" <alibuda@...ux.alibaba.com> To: Wenjia Zhang <wenjia@...ux.ibm.com>, kgraul@...ux.ibm.com, jaka@...ux.ibm.com, wintera@...ux.ibm.com Cc: kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org, linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org Subject: Re: [PATCH net 3/5] net/smc: allow cdc msg send rather than drop it with NULL sndbuf_desc On 10/12/23 4:37 AM, Wenjia Zhang wrote: > > > On 11.10.23 09:33, D. Wythe wrote: >> From: "D. Wythe" <alibuda@...ux.alibaba.com> >> >> This patch re-fix the issues memtianed by commit 22a825c541d7 >> ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()"). >> >> Blocking sending message do solve the issues though, but it also >> prevents the peer to receive the final message. Besides, in logic, >> whether the sndbuf_desc is NULL or not have no impact on the processing >> of cdc message sending. >> > Agree. > >> Hence that, this patch allow the cdc message sending but to check the >> sndbuf_desc with care in smc_cdc_tx_handler(). >> >> Fixes: 22a825c541d7 ("net/smc: fix NULL sndbuf_desc in >> smc_cdc_tx_handler()") >> Signed-off-by: D. Wythe <alibuda@...ux.alibaba.com> >> --- >> net/smc/smc_cdc.c | 9 ++++----- >> 1 file changed, 4 insertions(+), 5 deletions(-) >> >> diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c >> index 01bdb79..3c06625 100644 >> --- a/net/smc/smc_cdc.c >> +++ b/net/smc/smc_cdc.c >> @@ -28,13 +28,15 @@ static void smc_cdc_tx_handler(struct >> smc_wr_tx_pend_priv *pnd_snd, >> { >> struct smc_cdc_tx_pend *cdcpend = (struct smc_cdc_tx_pend >> *)pnd_snd; >> struct smc_connection *conn = cdcpend->conn; >> + struct smc_buf_desc *sndbuf_desc; >> struct smc_sock *smc; >> int diff; >> + sndbuf_desc = conn->sndbuf_desc; >> smc = container_of(conn, struct smc_sock, conn); >> bh_lock_sock(&smc->sk); >> - if (!wc_status) { >> - diff = smc_curs_diff(cdcpend->conn->sndbuf_desc->len, >> + if (!wc_status && sndbuf_desc) { >> + diff = smc_curs_diff(sndbuf_desc->len, > How could this guarantee that the sndbuf_desc would not be NULL? > It can not guarantee he sndbuf_desc would not be NULL, but it will prevents the smc_cdc_tx_handler() to access a NULL sndbuf_desc. So that we can avoid the panic descried in commit 22a825c541d7 ("net/smc: fix NULL sndbuf_desc in smc_cdc_tx_handler()"). >> &cdcpend->conn->tx_curs_fin, >> &cdcpend->cursor); >> /* sndbuf_space is decreased in smc_sendmsg */ >> @@ -114,9 +116,6 @@ int smc_cdc_msg_send(struct smc_connection *conn, >> union smc_host_cursor cfed; >> int rc; >> - if (unlikely(!READ_ONCE(conn->sndbuf_desc))) >> - return -ENOBUFS; >> - >> smc_cdc_add_pending_send(conn, pend); >> conn->tx_cdc_seq++;
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