From bb67093796a41e0f2601f5c0022fd8873ed59fee Mon Sep 17 00:00:00 2001
From: Michal Nazarewicz <mina86@mina86.com>
Date: Tue, 12 Nov 2013 15:11:42 -0800
Subject: [PATCH] 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>
---
drivers/w1/w1.c | 10 +++++-----
drivers/w1/w1.h | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/w1/w1.c b/drivers/w1/w1.c
index fa932c2f7d972..66efa96c46035 100644
--- a/drivers/w1/w1.c
+++ b/drivers/w1/w1.c
@@ -709,7 +709,7 @@ static int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
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 @@ void w1_slave_found(struct w1_master *dev, u64 rn)
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 @@ void w1_search_process_cb(struct w1_master *dev, u8 search_type,
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;
}
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 45908e56c2f83..ca8081a101d64 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -67,8 +67,8 @@ struct w1_slave
struct w1_reg_num reg_num;
atomic_t refcnt;
u8 rom[9];
- u32 flags;
int ttl;
+ unsigned long flags;
struct w1_master *master;
struct w1_family *family;
--
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