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![Tom Quetchenbach](/assets/img/avatar_default.png)
tcp_probe has a bounds-checking bug that causes many programs (less, python) to crash reading /proc/net/tcp_probe. When it outputs a log line to the reader, it only checks if that line alone will fit in the reader's buffer, rather than that line and all the previous lines it has already written. tcpprobe_read also returns the wrong value if copy_to_user fails--it just passes on the return value of copy_to_user (number of bytes not copied), which makes a failure look like a success. This patch fixes the buffer overflow and sets the return value to -EFAULT if copy_to_user fails. Patch is against latest net-2.6; tested briefly and seems to fix the crashes in less and python. Signed-off-by: Tom Quetchenbach <virtualphtn@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
254 lines
6 KiB
C
254 lines
6 KiB
C
/*
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* tcpprobe - Observe the TCP flow with kprobes.
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*
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* The idea for this came from Werner Almesberger's umlsim
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* Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
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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 by
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* the Free Software Foundation; either version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/kernel.h>
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#include <linux/kprobes.h>
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#include <linux/socket.h>
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#include <linux/tcp.h>
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/ktime.h>
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#include <linux/time.h>
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#include <net/net_namespace.h>
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#include <net/tcp.h>
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MODULE_AUTHOR("Stephen Hemminger <shemminger@linux-foundation.org>");
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MODULE_DESCRIPTION("TCP cwnd snooper");
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MODULE_LICENSE("GPL");
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MODULE_VERSION("1.1");
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static int port __read_mostly = 0;
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MODULE_PARM_DESC(port, "Port to match (0=all)");
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module_param(port, int, 0);
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static int bufsize __read_mostly = 4096;
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MODULE_PARM_DESC(bufsize, "Log buffer size in packets (4096)");
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module_param(bufsize, int, 0);
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static int full __read_mostly;
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MODULE_PARM_DESC(full, "Full log (1=every ack packet received, 0=only cwnd changes)");
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module_param(full, int, 0);
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static const char procname[] = "tcpprobe";
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struct tcp_log {
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ktime_t tstamp;
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__be32 saddr, daddr;
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__be16 sport, dport;
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u16 length;
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u32 snd_nxt;
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u32 snd_una;
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u32 snd_wnd;
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u32 snd_cwnd;
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u32 ssthresh;
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u32 srtt;
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};
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static struct {
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spinlock_t lock;
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wait_queue_head_t wait;
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ktime_t start;
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u32 lastcwnd;
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unsigned long head, tail;
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struct tcp_log *log;
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} tcp_probe;
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static inline int tcp_probe_used(void)
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{
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return (tcp_probe.head - tcp_probe.tail) % bufsize;
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}
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static inline int tcp_probe_avail(void)
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{
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return bufsize - tcp_probe_used();
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}
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/*
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* Hook inserted to be called before each receive packet.
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* Note: arguments must match tcp_rcv_established()!
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*/
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static int jtcp_rcv_established(struct sock *sk, struct sk_buff *skb,
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struct tcphdr *th, unsigned len)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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const struct inet_sock *inet = inet_sk(sk);
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/* Only update if port matches */
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if ((port == 0 || ntohs(inet->dport) == port || ntohs(inet->sport) == port)
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&& (full || tp->snd_cwnd != tcp_probe.lastcwnd)) {
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spin_lock(&tcp_probe.lock);
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/* If log fills, just silently drop */
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if (tcp_probe_avail() > 1) {
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struct tcp_log *p = tcp_probe.log + tcp_probe.head;
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p->tstamp = ktime_get();
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p->saddr = inet->saddr;
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p->sport = inet->sport;
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p->daddr = inet->daddr;
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p->dport = inet->dport;
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p->length = skb->len;
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p->snd_nxt = tp->snd_nxt;
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p->snd_una = tp->snd_una;
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p->snd_cwnd = tp->snd_cwnd;
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p->snd_wnd = tp->snd_wnd;
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p->ssthresh = tcp_current_ssthresh(sk);
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p->srtt = tp->srtt >> 3;
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tcp_probe.head = (tcp_probe.head + 1) % bufsize;
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}
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tcp_probe.lastcwnd = tp->snd_cwnd;
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spin_unlock(&tcp_probe.lock);
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wake_up(&tcp_probe.wait);
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}
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jprobe_return();
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return 0;
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}
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static struct jprobe tcp_jprobe = {
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.kp = {
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.symbol_name = "tcp_rcv_established",
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},
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.entry = jtcp_rcv_established,
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};
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static int tcpprobe_open(struct inode * inode, struct file * file)
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{
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/* Reset (empty) log */
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spin_lock_bh(&tcp_probe.lock);
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tcp_probe.head = tcp_probe.tail = 0;
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tcp_probe.start = ktime_get();
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spin_unlock_bh(&tcp_probe.lock);
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return 0;
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}
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static int tcpprobe_sprint(char *tbuf, int n)
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{
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const struct tcp_log *p
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= tcp_probe.log + tcp_probe.tail % bufsize;
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struct timespec tv
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= ktime_to_timespec(ktime_sub(p->tstamp, tcp_probe.start));
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return snprintf(tbuf, n,
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"%lu.%09lu " NIPQUAD_FMT ":%u " NIPQUAD_FMT ":%u"
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" %d %#x %#x %u %u %u %u\n",
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(unsigned long) tv.tv_sec,
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(unsigned long) tv.tv_nsec,
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NIPQUAD(p->saddr), ntohs(p->sport),
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NIPQUAD(p->daddr), ntohs(p->dport),
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p->length, p->snd_nxt, p->snd_una,
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p->snd_cwnd, p->ssthresh, p->snd_wnd, p->srtt);
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}
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static ssize_t tcpprobe_read(struct file *file, char __user *buf,
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size_t len, loff_t *ppos)
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{
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int error = 0, cnt = 0;
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if (!buf || len < 0)
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return -EINVAL;
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while (cnt < len) {
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char tbuf[128];
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int width;
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/* Wait for data in buffer */
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error = wait_event_interruptible(tcp_probe.wait,
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tcp_probe_used() > 0);
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if (error)
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break;
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spin_lock_bh(&tcp_probe.lock);
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if (tcp_probe.head == tcp_probe.tail) {
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/* multiple readers race? */
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spin_unlock_bh(&tcp_probe.lock);
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continue;
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}
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width = tcpprobe_sprint(tbuf, sizeof(tbuf));
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if (cnt + width < len)
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tcp_probe.tail = (tcp_probe.tail + 1) % bufsize;
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spin_unlock_bh(&tcp_probe.lock);
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/* if record greater than space available
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return partial buffer (so far) */
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if (cnt + width >= len)
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break;
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if (copy_to_user(buf + cnt, tbuf, width))
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return -EFAULT;
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cnt += width;
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}
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return cnt == 0 ? error : cnt;
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}
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static const struct file_operations tcpprobe_fops = {
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.owner = THIS_MODULE,
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.open = tcpprobe_open,
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.read = tcpprobe_read,
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};
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static __init int tcpprobe_init(void)
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{
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int ret = -ENOMEM;
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init_waitqueue_head(&tcp_probe.wait);
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spin_lock_init(&tcp_probe.lock);
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if (bufsize < 0)
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return -EINVAL;
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tcp_probe.log = kcalloc(sizeof(struct tcp_log), bufsize, GFP_KERNEL);
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if (!tcp_probe.log)
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goto err0;
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if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &tcpprobe_fops))
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goto err0;
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ret = register_jprobe(&tcp_jprobe);
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if (ret)
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goto err1;
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pr_info("TCP probe registered (port=%d)\n", port);
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return 0;
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err1:
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proc_net_remove(&init_net, procname);
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err0:
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kfree(tcp_probe.log);
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return ret;
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}
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module_init(tcpprobe_init);
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static __exit void tcpprobe_exit(void)
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{
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proc_net_remove(&init_net, procname);
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unregister_jprobe(&tcp_jprobe);
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kfree(tcp_probe.log);
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}
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module_exit(tcpprobe_exit);
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