drivers: w1: make w1_slave::flags long to avoid memory corruption
On architectures where long is more then 32 bits, modifying a 32-bit field
with set_bit (and other atomic bit operations) may cause bytes following
the field to by modified.
Because the endianness of the bits within a field is the native endianness
of the CPU[1], on big-endian machines, bit number zero is in the last byte
of the field.
Therefore, `set_bit(0, ptr)' on a 64-bit big-endian machine is roughly
equivalent to `((char *)ptr)[7] |= 1', and since w1 driver uses a 32-bit
field for holding the flags, this causes bytes beyond the field to be
modified.
[1] From Documentation/atomic_ops.txt:
Native atomic bit operations are defined to operate on objects
aligned to the size of an "unsigned long" C data type, and are
least of that size. The endianness of the bits within each
"unsigned long" are the native endianness of the cpu.
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index fa932c2..66efa96 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -709,7 +709,7 @@
sl->owner = THIS_MODULE;
sl->master = dev;
- set_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
+ set_bit(W1_SLAVE_ACTIVE, &sl->flags);
memset(&msg, 0, sizeof(msg));
memcpy(&sl->reg_num, rn, sizeof(sl->reg_num));
@@ -866,7 +866,7 @@
sl = w1_slave_search_device(dev, tmp);
if (sl) {
- set_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
+ set_bit(W1_SLAVE_ACTIVE, &sl->flags);
} else {
if (rn && tmp->crc == w1_calc_crc8((u8 *)&rn_le, 7))
w1_attach_slave_device(dev, tmp);
@@ -984,14 +984,14 @@
struct w1_slave *sl, *sln;
list_for_each_entry(sl, &dev->slist, w1_slave_entry)
- clear_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
+ clear_bit(W1_SLAVE_ACTIVE, &sl->flags);
w1_search_devices(dev, search_type, cb);
list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
- if (!test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags) && !--sl->ttl)
+ if (!test_bit(W1_SLAVE_ACTIVE, &sl->flags) && !--sl->ttl)
w1_slave_detach(sl);
- else if (test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags))
+ else if (test_bit(W1_SLAVE_ACTIVE, &sl->flags))
sl->ttl = dev->slave_ttl;
}