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V4L/DVB (7580): Fix concurrent read from /proc/videocodecs

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Observation one: ->write_proc and ->data assignments aren't needed. Removed.
Observation two: codecs lists are unprotected. Patch doesn't fix this.
Observation three:
	/proc/videocodecs printout is done to temporary _global_ buffer which
	is freed in between. Consequently, two users hitting this file can
	screwup each other.

Steps to reproduce:

	modprobe videocodec
	while true; do cat /proc/videocodecs &>/dev/null; done &
	while true; do cat /proc/videocodecs &>/dev/null; done &

The fix is switching to seq_files, this removes code, especially some
line-length "logic".

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
This commit is contained in:
Alexey Dobriyan 2008-04-13 08:48:43 -03:00 committed by Mauro Carvalho Chehab
parent b9bc07a006
commit 9faa2d7582
1 changed files with 19 additions and 94 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

113
drivers/media/video/videocodec.c
View File

@ -39,6 +39,7 @@
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>
#endif
@ -320,56 +321,22 @@ videocodec_unregister (const struct videocodec *codec)
}
#ifdef CONFIG_PROC_FS
/* ============ */
/* procfs stuff */
/* ============ */
static char *videocodec_buf = NULL;
static int videocodec_bufsize;
static int
videocodec_build_table (void)
static int proc_videocodecs_show(struct seq_file *m, void *v)
{
struct codec_list *h = codeclist_top;
struct attached_list *a;
int i = 0, size;
// sum up amount of slaves plus their attached masters
while (h) {
i += h->attached + 1;
h = h->next;
}
#define LINESIZE 100
size = LINESIZE * (i + 1);
dprintk(3, "videocodec_build table: %d entries, %d bytes\n", i,
size);
kfree(videocodec_buf);
videocodec_buf = kmalloc(size, GFP_KERNEL);
if (!videocodec_buf)
return 0;
i = 0;
i += scnprintf(videocodec_buf + i, size - 1,
"<S>lave or attached <M>aster name type flags magic ");
i += scnprintf(videocodec_buf + i, size -i - 1, "(connected as)\n");
seq_printf(m, "<S>lave or attached <M>aster name type flags magic ");
seq_printf(m, "(connected as)\n");
h = codeclist_top;
while (h) {
if (i > (size - LINESIZE))
break; // security check
i += scnprintf(videocodec_buf + i, size -i -1,
"S %32s %04x %08lx %08lx (TEMPLATE)\n",
seq_printf(m, "S %32s %04x %08lx %08lx (TEMPLATE)\n",
h->codec->name, h->codec->type,
h->codec->flags, h->codec->magic);
a = h->list;
while (a) {
if (i > (size - LINESIZE))
break; // security check
i += scnprintf(videocodec_buf + i, size -i -1,
"M %32s %04x %08lx %08lx (%s)\n",
seq_printf(m, "M %32s %04x %08lx %08lx (%s)\n",
a->codec->master_data->name,
a->codec->master_data->type,
a->codec->master_data->flags,
@ -380,54 +347,21 @@ videocodec_build_table (void)
h = h->next;
}
return i;
return 0;
}
//The definition:
//typedef int (read_proc_t)(char *page, char **start, off_t off,
// int count, int *eof, void *data);
static int
videocodec_info (char *buffer,
char **buffer_location,
off_t offset,
int buffer_length,
int *eof,
void *data)
static int proc_videocodecs_open(struct inode *inode, struct file *file)
{
int size;
dprintk(3, "videocodec_info: offset: %ld, len %d / size %d\n",
offset, buffer_length, videocodec_bufsize);
if (offset == 0) {
videocodec_bufsize = videocodec_build_table();
}
if ((offset < 0) || (offset >= videocodec_bufsize)) {
dprintk(4,
"videocodec_info: call delivers no result, return 0\n");
*eof = 1;
return 0;
}
if (buffer_length < (videocodec_bufsize - offset)) {
dprintk(4, "videocodec_info: %ld needed, %d got\n",
videocodec_bufsize - offset, buffer_length);
size = buffer_length;
} else {
dprintk(4, "videocodec_info: last reading of %ld bytes\n",
videocodec_bufsize - offset);
size = videocodec_bufsize - offset;
*eof = 1;
}
memcpy(buffer, videocodec_buf + offset, size);
/* doesn't work... */
/* copy_to_user(buffer, videocodec_buf+offset, size); */
/* *buffer_location = videocodec_buf+offset; */
return size;
return single_open(file, proc_videocodecs_show, NULL);
}
static const struct file_operations videocodecs_proc_fops = {
.owner = THIS_MODULE,
.open = proc_videocodecs_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
#endif
/* ===================== */
@ -444,16 +378,8 @@ videocodec_init (void)
VIDEOCODEC_VERSION);
#ifdef CONFIG_PROC_FS
videocodec_buf = NULL;
videocodec_bufsize = 0;
videocodec_proc_entry = create_proc_entry("videocodecs", 0, NULL);
if (videocodec_proc_entry) {
videocodec_proc_entry->read_proc = videocodec_info;
videocodec_proc_entry->write_proc = NULL;
videocodec_proc_entry->data = NULL;
videocodec_proc_entry->owner = THIS_MODULE;
} else {
videocodec_proc_entry = proc_create("videocodecs", 0, NULL, &videocodecs_proc_fops);
if (!videocodec_proc_entry) {
dprintk(1, KERN_ERR "videocodec: can't init procfs.\n");
}
#endif
@ -465,7 +391,6 @@ videocodec_exit (void)
{
#ifdef CONFIG_PROC_FS
remove_proc_entry("videocodecs", NULL);
kfree(videocodec_buf);
#endif
}