From: Stefan Metzmacher Date: Thu, 22 Jan 2026 17:16:46 +0000 (+0100) Subject: smb: server: fix last send credit problem causing disconnects X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8cf2bbac6281434065f5f3aeab19c9c08ff755a2;p=thirdparty%2Fkernel%2Fstable.git smb: server: fix last send credit problem causing disconnects When we are about to use the last send credit that was granted to us by the peer, we need to wait until we are ourself able to grant at least one credit to the peer. Otherwise it might not be possible for the peer to grant more credits. The following sections in MS-SMBD are related to this: 3.1.5.1 Sending Upper Layer Messages ... If Connection.SendCredits is 1 and the CreditsGranted field of the message is 0, stop processing. ... 3.1.5.9 Managing Credits Prior to Sending ... If Connection.ReceiveCredits is zero, or if Connection.SendCredits is one and the Connection.SendQueue is not empty, the sender MUST allocate and post at least one receive of size Connection.MaxReceiveSize and MUST increment Connection.ReceiveCredits by the number allocated and posted. If no receives are posted, the processing MUST return a value of zero to indicate to the caller that no Send message can be currently performed. ... This problem was found by running this on Windows 2025 against ksmbd with required smb signing: 'frametest.exe -r 4k -t 20 -n 2000' after 'frametest.exe -w 4k -t 20 -n 2000'. Link: https://lore.kernel.org/linux-cifs/b58fa352-2386-4145-b42e-9b4b1d484e17@samba.org/ Cc: # 6.18.x Cc: Namjae Jeon Cc: Steve French Cc: Tom Talpey Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Signed-off-by: Stefan Metzmacher Acked-by: Namjae Jeon Signed-off-by: Steve French --- diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c index 38248b6a1b5c..5c0cc5064e8c 100644 --- a/fs/smb/server/transport_rdma.c +++ b/fs/smb/server/transport_rdma.c @@ -1033,6 +1033,15 @@ static void smb_direct_post_recv_credits(struct work_struct *work) atomic_add(credits, &sc->recv_io.credits.available); + /* + * If the last send credit is waiting for credits + * it can grant we need to wake it up + */ + if (credits && + atomic_read(&sc->send_io.bcredits.count) == 0 && + atomic_read(&sc->send_io.credits.count) == 0) + wake_up(&sc->send_io.credits.wait_queue); + if (credits) queue_work(sc->workqueue, &sc->idle.immediate_work); } @@ -1306,6 +1315,7 @@ static int calc_rw_credits(struct smbdirect_socket *sc, static int smb_direct_create_header(struct smbdirect_socket *sc, int size, int remaining_data_length, + int new_credits, struct smbdirect_send_io **sendmsg_out) { struct smbdirect_socket_parameters *sp = &sc->parameters; @@ -1321,7 +1331,7 @@ static int smb_direct_create_header(struct smbdirect_socket *sc, /* Fill in the packet header */ packet = (struct smbdirect_data_transfer *)sendmsg->packet; packet->credits_requested = cpu_to_le16(sp->send_credit_target); - packet->credits_granted = cpu_to_le16(manage_credits_prior_sending(sc)); + packet->credits_granted = cpu_to_le16(new_credits); packet->flags = 0; if (manage_keep_alive_before_sending(sc)) @@ -1459,6 +1469,7 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc, int data_length; struct scatterlist sg[SMBDIRECT_SEND_IO_MAX_SGE - 1]; struct smbdirect_send_batch _send_ctx; + int new_credits; if (!send_ctx) { smb_direct_send_ctx_init(&_send_ctx, false, 0); @@ -1477,12 +1488,29 @@ static int smb_direct_post_send_data(struct smbdirect_socket *sc, if (ret) goto credit_failed; + new_credits = manage_credits_prior_sending(sc); + if (new_credits == 0 && + atomic_read(&sc->send_io.credits.count) == 0 && + atomic_read(&sc->recv_io.credits.count) == 0) { + queue_work(sc->workqueue, &sc->recv_io.posted.refill_work); + ret = wait_event_interruptible(sc->send_io.credits.wait_queue, + atomic_read(&sc->send_io.credits.count) >= 1 || + atomic_read(&sc->recv_io.credits.available) >= 1 || + sc->status != SMBDIRECT_SOCKET_CONNECTED); + if (sc->status != SMBDIRECT_SOCKET_CONNECTED) + ret = -ENOTCONN; + if (ret < 0) + goto credit_failed; + + new_credits = manage_credits_prior_sending(sc); + } + data_length = 0; for (i = 0; i < niov; i++) data_length += iov[i].iov_len; ret = smb_direct_create_header(sc, data_length, remaining_data_length, - &msg); + new_credits, &msg); if (ret) goto header_failed;