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https://github.com/torvalds/linux
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7963256961
There is a general misunderstanding amongst engineers that {v}snprintf()
returns the length of the data *actually* encoded into the destination
array. However, as per the C99 standard {v}snprintf() really returns
the length of the data that *would have been* written if there were
enough space for it. This misunderstanding has led to buffer-overruns
in the past. It's generally considered safer to use the {v}scnprintf()
variants in their place (or even sprintf() in simple cases). So let's
do that.
Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20231213164246.1021885-10-lee@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
72 lines
1.6 KiB
C
72 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* The USB Monitor, inspired by Dave Harding's USBMon.
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*
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* This is the 's' or 'stat' reader which debugs usbmon itself.
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* Note that this code blows through locks, so make sure that
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* /dbg/usbmon/0s is well protected from non-root users.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/export.h>
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#include <linux/usb.h>
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#include <linux/fs.h>
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#include <linux/uaccess.h>
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#include "usb_mon.h"
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#define STAT_BUF_SIZE 80
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struct snap {
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int slen;
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char str[STAT_BUF_SIZE];
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};
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static int mon_stat_open(struct inode *inode, struct file *file)
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{
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struct mon_bus *mbus;
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struct snap *sp;
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sp = kmalloc(sizeof(struct snap), GFP_KERNEL);
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if (sp == NULL)
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return -ENOMEM;
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mbus = inode->i_private;
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sp->slen = scnprintf(sp->str, STAT_BUF_SIZE,
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"nreaders %d events %u text_lost %u\n",
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mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);
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file->private_data = sp;
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return 0;
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}
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static ssize_t mon_stat_read(struct file *file, char __user *buf,
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size_t nbytes, loff_t *ppos)
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{
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struct snap *sp = file->private_data;
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return simple_read_from_buffer(buf, nbytes, ppos, sp->str, sp->slen);
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}
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static int mon_stat_release(struct inode *inode, struct file *file)
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{
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struct snap *sp = file->private_data;
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file->private_data = NULL;
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kfree(sp);
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return 0;
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}
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const struct file_operations mon_fops_stat = {
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.owner = THIS_MODULE,
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.open = mon_stat_open,
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.llseek = no_llseek,
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.read = mon_stat_read,
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/* .write = mon_stat_write, */
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/* .poll = mon_stat_poll, */
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/* .unlocked_ioctl = mon_stat_ioctl, */
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.release = mon_stat_release,
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};
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