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W1: w1_therm fix user buffer overflow and cat

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Fixed data reading bug by replacing binary attribute with device one.

Switching the sysfs read from bin_attribute to device_attribute.  The data
is far under PAGE_SIZE so the binary interface isn't required.  As the
device_attribute interface will make one call to w1_therm_read per file
open and buffer, the result is, the following problems go away.

buffer overflow:
	Execute a short read on w1_slave and w1_therm_read_bin would still
	return the full string size worth of data clobbering the user space
	buffer when it returned.  Switching to device_attribute avoids the
	buffer overflow problems.  With the snprintf formatted output dealing
	with short reads without doing a conversion per read would have
	been difficult.
bad behavior:
	`cat w1_slave` would cause two temperature conversions to take place.
	Previously the code assumed W1_SLAVE_DATA_SIZE would be returned with
	each read.  It would not return 0 unless the offset was less
	than W1_SLAVE_DATA_SIZE.  The result was the first read did a
	temperature conversion, filled the buffer and returned, the
	offset in the second read would be less than
	W1_SLAVE_DATA_SIZE and also fill the buffer and return, the
	third read would finnally have a big enough offset to return 0
	and cause cat to stop.  Now w1_therm_read will be called at
	most once per open.

Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Fries 2008-10-15 22:04:51 -07:00 committed by Linus Torvalds
parent 07e003417b
commit 347ba8a588
2 changed files with 20 additions and 36 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

55
drivers/w1/slaves/w1_therm.c
View file

@ -50,26 +50,20 @@ static u8 bad_roms[][9] = {
{}
};
static ssize_t w1_therm_read_bin(struct kobject *, struct bin_attribute *,
char *, loff_t, size_t);
static ssize_t w1_therm_read(struct device *device,
struct device_attribute *attr, char *buf);
static struct bin_attribute w1_therm_bin_attr = {
.attr = {
.name = "w1_slave",
.mode = S_IRUGO,
},
.size = W1_SLAVE_DATA_SIZE,
.read = w1_therm_read_bin,
};
static struct device_attribute w1_therm_attr =
__ATTR(w1_slave, S_IRUGO, w1_therm_read, NULL);
static int w1_therm_add_slave(struct w1_slave *sl)
{
return sysfs_create_bin_file(&sl->dev.kobj, &w1_therm_bin_attr);
return device_create_file(&sl->dev, &w1_therm_attr);
}
static void w1_therm_remove_slave(struct w1_slave *sl)
{
sysfs_remove_bin_file(&sl->dev.kobj, &w1_therm_bin_attr);
device_remove_file(&sl->dev, &w1_therm_attr);
}
static struct w1_family_ops w1_therm_fops = {
@ -168,30 +162,19 @@ static int w1_therm_check_rom(u8 rom[9])
return 0;
}
static ssize_t w1_therm_read_bin(struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buf, loff_t off, size_t count)
static ssize_t w1_therm_read(struct device *device,
struct device_attribute *attr, char *buf)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
struct w1_slave *sl = dev_to_w1_slave(device);
struct w1_master *dev = sl->master;
u8 rom[9], crc, verdict;
int i, max_trying = 10;
ssize_t c = PAGE_SIZE;
mutex_lock(&sl->master->mutex);
if (off > W1_SLAVE_DATA_SIZE) {
count = 0;
goto out;
}
if (off + count > W1_SLAVE_DATA_SIZE) {
count = 0;
goto out;
}
memset(buf, 0, count);
memset(rom, 0, sizeof(rom));
count = 0;
verdict = 0;
crc = 0;
@ -211,7 +194,9 @@ static ssize_t w1_therm_read_bin(struct kobject *kobj,
w1_write_8(dev, W1_READ_SCRATCHPAD);
if ((count = w1_read_block(dev, rom, 9)) != 9) {
dev_warn(&dev->dev, "w1_read_block() returned %d instead of 9.\n", count);
dev_warn(device, "w1_read_block() "
"returned %u instead of 9.\n",
count);
}
crc = w1_calc_crc8(rom, 8);
@ -226,22 +211,22 @@ static ssize_t w1_therm_read_bin(struct kobject *kobj,
}
for (i = 0; i < 9; ++i)
count += sprintf(buf + count, "%02x ", rom[i]);
count += sprintf(buf + count, ": crc=%02x %s\n",
c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", rom[i]);
c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
crc, (verdict) ? "YES" : "NO");
if (verdict)
memcpy(sl->rom, rom, sizeof(sl->rom));
else
dev_warn(&dev->dev, "18S20 doesn't respond to CONVERT_TEMP.\n");
dev_warn(device, "18S20 doesn't respond to CONVERT_TEMP.\n");
for (i = 0; i < 9; ++i)
count += sprintf(buf + count, "%02x ", sl->rom[i]);
c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", sl->rom[i]);
count += sprintf(buf + count, "t=%d\n", w1_convert_temp(rom, sl->family->fid));
out:
c -= snprintf(buf + PAGE_SIZE - c, c, "t=%d\n",
w1_convert_temp(rom, sl->family->fid));
mutex_unlock(&dev->mutex);
return count;
return PAGE_SIZE - c;
}
static int __init w1_therm_init(void)

1
drivers/w1/w1.h
View file

@ -46,7 +46,6 @@ struct w1_reg_num
#include "w1_family.h"
#define W1_MAXNAMELEN 32
#define W1_SLAVE_DATA_SIZE 128
#define W1_SEARCH 0xF0
#define W1_ALARM_SEARCH 0xEC