W1: w1_therm fix user buffer overflow and cat

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>

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index e87f464..7de99df 100644 (file)
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -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)

diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 00b84ab..cdaa6ff 100644 (file)
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -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