Revision 712f3147aee0fbbbbed2da20b21b272c5505125e authored by Linus Torvalds on 13 May 2011, 23:16:41 UTC, committed by Linus Torvalds on 14 May 2011, 17:23:44 UTC
When a register_framebuffer() call results in us removing old conflicting framebuffers, the new registration_lock doesn't protect that situation. And we can't just add the same locking to the function, because these functions call each other: register_framebuffer() calls remove_conflicting_framebuffers, which in turn calls unregister_framebuffer for any conflicting entry. In order to fix it, this just creates wrapper functions around all three functions and makes the versions that actually do the work be called "do_xxx()", leaving just the wrapper that gets the lock and calls the worker function. So the rule becomes simply that "do_xxxx()" has to be called with the lock held, and now do_register_framebuffer() can just call do_remove_conflicting_framebuffers(), and that in turn can call _do_unregister_framebuffer(), and there is no deadlock, and we can hold the registration lock over the whole sequence, fixing the races. It also makes error cases simpler, and fixes one situation where we would return from unregister_framebuffer() without releasing the lock, pointed out by Bruno Prémont. Tested-by: Bruno Prémont <bonbons@linux-vserver.org> Tested-by: Anca Emanuel <anca.emanuel@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent c47747f
probe.c
/*
* dccp_probe - Observe the DCCP flow with kprobes.
*
* The idea for this came from Werner Almesberger's umlsim
* Copyright (C) 2004, Stephen Hemminger <shemminger@osdl.org>
*
* Modified for DCCP from Stephen Hemminger's code
* Copyright (C) 2006, Ian McDonald <ian.mcdonald@jandi.co.nz>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/socket.h>
#include <linux/dccp.h>
#include <linux/proc_fs.h>
#include <linux/module.h>
#include <linux/kfifo.h>
#include <linux/vmalloc.h>
#include <linux/gfp.h>
#include <net/net_namespace.h>
#include "dccp.h"
#include "ccid.h"
#include "ccids/ccid3.h"
static int port;
static int bufsize = 64 * 1024;
static const char procname[] = "dccpprobe";
static struct {
struct kfifo fifo;
spinlock_t lock;
wait_queue_head_t wait;
struct timespec tstart;
} dccpw;
static void printl(const char *fmt, ...)
{
va_list args;
int len;
struct timespec now;
char tbuf[256];
va_start(args, fmt);
getnstimeofday(&now);
now = timespec_sub(now, dccpw.tstart);
len = sprintf(tbuf, "%lu.%06lu ",
(unsigned long) now.tv_sec,
(unsigned long) now.tv_nsec / NSEC_PER_USEC);
len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
va_end(args);
kfifo_in_locked(&dccpw.fifo, tbuf, len, &dccpw.lock);
wake_up(&dccpw.wait);
}
static int jdccp_sendmsg(struct kiocb *iocb, struct sock *sk,
struct msghdr *msg, size_t size)
{
const struct inet_sock *inet = inet_sk(sk);
struct ccid3_hc_tx_sock *hc = NULL;
if (ccid_get_current_tx_ccid(dccp_sk(sk)) == DCCPC_CCID3)
hc = ccid3_hc_tx_sk(sk);
if (port == 0 || ntohs(inet->inet_dport) == port ||
ntohs(inet->inet_sport) == port) {
if (hc)
printl("%pI4:%u %pI4:%u %d %d %d %d %u %llu %llu %d\n",
&inet->inet_saddr, ntohs(inet->inet_sport),
&inet->inet_daddr, ntohs(inet->inet_dport), size,
hc->tx_s, hc->tx_rtt, hc->tx_p,
hc->tx_x_calc, hc->tx_x_recv >> 6,
hc->tx_x >> 6, hc->tx_t_ipi);
else
printl("%pI4:%u %pI4:%u %d\n",
&inet->inet_saddr, ntohs(inet->inet_sport),
&inet->inet_daddr, ntohs(inet->inet_dport),
size);
}
jprobe_return();
return 0;
}
static struct jprobe dccp_send_probe = {
.kp = {
.symbol_name = "dccp_sendmsg",
},
.entry = jdccp_sendmsg,
};
static int dccpprobe_open(struct inode *inode, struct file *file)
{
kfifo_reset(&dccpw.fifo);
getnstimeofday(&dccpw.tstart);
return 0;
}
static ssize_t dccpprobe_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
int error = 0, cnt = 0;
unsigned char *tbuf;
if (!buf)
return -EINVAL;
if (len == 0)
return 0;
tbuf = vmalloc(len);
if (!tbuf)
return -ENOMEM;
error = wait_event_interruptible(dccpw.wait,
kfifo_len(&dccpw.fifo) != 0);
if (error)
goto out_free;
cnt = kfifo_out_locked(&dccpw.fifo, tbuf, len, &dccpw.lock);
error = copy_to_user(buf, tbuf, cnt) ? -EFAULT : 0;
out_free:
vfree(tbuf);
return error ? error : cnt;
}
static const struct file_operations dccpprobe_fops = {
.owner = THIS_MODULE,
.open = dccpprobe_open,
.read = dccpprobe_read,
.llseek = noop_llseek,
};
static __init int dccpprobe_init(void)
{
int ret = -ENOMEM;
init_waitqueue_head(&dccpw.wait);
spin_lock_init(&dccpw.lock);
if (kfifo_alloc(&dccpw.fifo, bufsize, GFP_KERNEL))
return ret;
if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &dccpprobe_fops))
goto err0;
try_then_request_module((ret = register_jprobe(&dccp_send_probe)) == 0,
"dccp");
if (ret)
goto err1;
pr_info("DCCP watch registered (port=%d)\n", port);
return 0;
err1:
proc_net_remove(&init_net, procname);
err0:
kfifo_free(&dccpw.fifo);
return ret;
}
module_init(dccpprobe_init);
static __exit void dccpprobe_exit(void)
{
kfifo_free(&dccpw.fifo);
proc_net_remove(&init_net, procname);
unregister_jprobe(&dccp_send_probe);
}
module_exit(dccpprobe_exit);
MODULE_PARM_DESC(port, "Port to match (0=all)");
module_param(port, int, 0);
MODULE_PARM_DESC(bufsize, "Log buffer size (default 64k)");
module_param(bufsize, int, 0);
MODULE_AUTHOR("Ian McDonald <ian.mcdonald@jandi.co.nz>");
MODULE_DESCRIPTION("DCCP snooper");
MODULE_LICENSE("GPL");
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