505f76b306
There is a race condition in iscsi_tcp.c that may cause it to forget
that it received a R2T from the target. This race may cause a data-out
command (such as a write) to lock up. The race occurs here:
static int
iscsi_send_unsol_pdu(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
struct iscsi_tcp_cmd_task *tcp_ctask = ctask->dd_data;
int rc;
if (tcp_ctask->xmstate & XMSTATE_UNS_HDR) {
BUG_ON(!ctask->unsol_count);
tcp_ctask->xmstate &= ~XMSTATE_UNS_HDR; <---- RACE
...
static int
iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
{
...
tcp_ctask->xmstate |= XMSTATE_SOL_HDR_INIT; <---- RACE
...
While iscsi_xmitworker() (called from scsi_queue_work()) is preparing to
send unsolicited data, iscsi_tcp_data_recv() (called from
tcp_read_sock()) interrupts it upon receipt of a R2T from the target.
Both contexts do read-modify-write of tcp_ctask->xmstate. Usually, gcc
on x86 will make &= and |= atomic on UP (not guaranteed of course), but
in this case iscsi_send_unsol_pdu() reads the value of xmstate before
clearing the bit, which causes gcc to read xmstate into a CPU register,
test it, clear the bit, and then store it back to memory. If the recv
interrupt happens during this sequence, then the XMSTATE_SOL_HDR_INIT
bit set by the recv interrupt will be lost, and the R2T will be
forgotten.
The patch below (against 2.6.24-rc1) converts accesses of xmstate to use
set_bit, clear_bit, and test_bit instead of |= and &=. I have tested
this patch and verified that it fixes the problem. Another possible
approach would be to hold a lock during most of the rx/tx setup and
post-processing, and drop the lock only for the actual rx/tx.
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
170 lines
5.1 KiB
C
170 lines
5.1 KiB
C
/*
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* iSCSI Initiator TCP Transport
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* Copyright (C) 2004 Dmitry Yusupov
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* Copyright (C) 2004 Alex Aizman
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* Copyright (C) 2005 - 2006 Mike Christie
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* Copyright (C) 2006 Red Hat, Inc. All rights reserved.
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* maintained by open-iscsi@googlegroups.com
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* See the file COPYING included with this distribution for more details.
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*/
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#ifndef ISCSI_TCP_H
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#define ISCSI_TCP_H
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#include <scsi/libiscsi.h>
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/* Socket's Receive state machine */
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#define IN_PROGRESS_WAIT_HEADER 0x0
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#define IN_PROGRESS_HEADER_GATHER 0x1
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#define IN_PROGRESS_DATA_RECV 0x2
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#define IN_PROGRESS_DDIGEST_RECV 0x3
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#define IN_PROGRESS_PAD_RECV 0x4
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/* xmit state machine */
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#define XMSTATE_VALUE_IDLE 0
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#define XMSTATE_BIT_CMD_HDR_INIT 0
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#define XMSTATE_BIT_CMD_HDR_XMIT 1
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#define XMSTATE_BIT_IMM_HDR 2
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#define XMSTATE_BIT_IMM_DATA 3
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#define XMSTATE_BIT_UNS_INIT 4
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#define XMSTATE_BIT_UNS_HDR 5
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#define XMSTATE_BIT_UNS_DATA 6
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#define XMSTATE_BIT_SOL_HDR 7
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#define XMSTATE_BIT_SOL_DATA 8
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#define XMSTATE_BIT_W_PAD 9
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#define XMSTATE_BIT_W_RESEND_PAD 10
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#define XMSTATE_BIT_W_RESEND_DATA_DIGEST 11
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#define XMSTATE_BIT_IMM_HDR_INIT 12
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#define XMSTATE_BIT_SOL_HDR_INIT 13
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#define ISCSI_PAD_LEN 4
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#define ISCSI_SG_TABLESIZE SG_ALL
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#define ISCSI_TCP_MAX_CMD_LEN 16
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struct crypto_hash;
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struct socket;
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/* Socket connection recieve helper */
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struct iscsi_tcp_recv {
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struct iscsi_hdr *hdr;
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struct sk_buff *skb;
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int offset;
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int len;
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int hdr_offset;
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int copy;
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int copied;
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int padding;
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struct iscsi_cmd_task *ctask; /* current cmd in progress */
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/* copied and flipped values */
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int datalen;
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int datadgst;
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char zero_copy_hdr;
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};
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struct iscsi_tcp_conn {
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struct iscsi_conn *iscsi_conn;
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struct socket *sock;
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struct iscsi_hdr hdr; /* header placeholder */
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char hdrext[4*sizeof(__u16) +
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sizeof(__u32)];
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int data_copied;
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int stop_stage; /* conn_stop() flag: *
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* stop to recover, *
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* stop to terminate */
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/* iSCSI connection-wide sequencing */
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int hdr_size; /* PDU header size */
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/* control data */
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struct iscsi_tcp_recv in; /* TCP receive context */
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int in_progress; /* connection state machine */
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/* old values for socket callbacks */
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void (*old_data_ready)(struct sock *, int);
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void (*old_state_change)(struct sock *);
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void (*old_write_space)(struct sock *);
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/* data and header digests */
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struct hash_desc tx_hash; /* CRC32C (Tx) */
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struct hash_desc rx_hash; /* CRC32C (Rx) */
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/* MIB custom statistics */
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uint32_t sendpage_failures_cnt;
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uint32_t discontiguous_hdr_cnt;
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ssize_t (*sendpage)(struct socket *, struct page *, int, size_t, int);
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};
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struct iscsi_buf {
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struct scatterlist sg;
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unsigned int sent;
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char use_sendmsg;
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};
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struct iscsi_data_task {
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struct iscsi_data hdr; /* PDU */
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char hdrext[sizeof(__u32)]; /* Header-Digest */
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struct iscsi_buf digestbuf; /* digest buffer */
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uint32_t digest; /* data digest */
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};
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struct iscsi_tcp_mgmt_task {
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struct iscsi_hdr hdr;
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char hdrext[sizeof(__u32)]; /* Header-Digest */
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unsigned long xmstate; /* mgmt xmit progress */
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struct iscsi_buf headbuf; /* header buffer */
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struct iscsi_buf sendbuf; /* in progress buffer */
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int sent;
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};
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struct iscsi_r2t_info {
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__be32 ttt; /* copied from R2T */
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__be32 exp_statsn; /* copied from R2T */
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uint32_t data_length; /* copied from R2T */
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uint32_t data_offset; /* copied from R2T */
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struct iscsi_buf headbuf; /* Data-Out Header Buffer */
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struct iscsi_buf sendbuf; /* Data-Out in progress buffer*/
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int sent; /* R2T sequence progress */
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int data_count; /* DATA-Out payload progress */
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struct scatterlist *sg; /* per-R2T SG list */
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int solicit_datasn;
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struct iscsi_data_task dtask; /* which data task */
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};
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struct iscsi_tcp_cmd_task {
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struct iscsi_cmd hdr;
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char hdrext[4*sizeof(__u16)+ /* AHS */
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sizeof(__u32)]; /* HeaderDigest */
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char pad[ISCSI_PAD_LEN];
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int pad_count; /* padded bytes */
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struct iscsi_buf headbuf; /* header buf (xmit) */
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struct iscsi_buf sendbuf; /* in progress buffer*/
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unsigned long xmstate; /* xmit xtate machine */
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int sent;
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struct scatterlist *sg; /* per-cmd SG list */
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struct scatterlist *bad_sg; /* assert statement */
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int sg_count; /* SG's to process */
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uint32_t exp_datasn; /* expected target's R2TSN/DataSN */
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int data_offset;
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struct iscsi_r2t_info *r2t; /* in progress R2T */
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struct iscsi_queue r2tpool;
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struct kfifo *r2tqueue;
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struct iscsi_r2t_info **r2ts;
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int digest_count;
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uint32_t immdigest; /* for imm data */
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struct iscsi_buf immbuf; /* for imm data digest */
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struct iscsi_data_task unsol_dtask; /* unsol data task */
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};
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#endif /* ISCSI_H */
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