bluetooth: don't use bitmaps for random flag accesses

The bluetooth code uses our bitmap infrastructure for the two bits (!)
of connection setup flags, and in the process causes odd problems when
it converts between a bitmap and just the regular values of said bits.

It's completely pointless to do things like bitmap_to_arr32() to convert
a bitmap into a u32.  It shoudln't have been a bitmap in the first
place.  The reason to use bitmaps is if you have arbitrary number of
bits you want to manage (not two!), or if you rely on the atomicity
guarantees of the bitmap setting and clearing.

The code could use an "atomic_t" and use "atomic_or/andnot()" to set and
clear the bit values, but considering that it then copies the bitmaps
around with "bitmap_to_arr32()" and friends, there clearly cannot be a
lot of atomicity requirements.

So just use a regular integer.

In the process, this avoids the warnings about erroneous use of
bitmap_from_u64() which were triggered on 32-bit architectures when
conversion from a u64 would access two words (and, surprise, surprise,
only one word is needed - and indeed overkill - for a 2-bit bitmap).

That was always problematic, but the compiler seems to notice it and
warn about the invalid pattern only after commit 0a97953fd221 ("lib: add
bitmap_{from,to}_arr64") changed the exact implementation details of
'bitmap_from_u64()', as reported by Sudip Mukherjee and Stephen Rothwell.

Fixes: fe92ee6425a2 ("Bluetooth: hci_core: Rework hci_conn_params flags")
Link: https://lore.kernel.org/all/YpyJ9qTNHJzz0FHY@debian/
Link: https://lore.kernel.org/all/20220606080631.0c3014f2@canb.auug.org.au/
Link: https://lore.kernel.org/all/20220605162537.1604762-1-yury.norov@gmail.com/
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 10 deletions

diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index 5a52a2018b56..c0ea2a4892b1 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -155,21 +155,18 @@ struct bdaddr_list_with_irk {
 	u8 local_irk[16];
 };
 
+/* Bitmask of connection flags */
 enum hci_conn_flags {
-	HCI_CONN_FLAG_REMOTE_WAKEUP,
-	HCI_CONN_FLAG_DEVICE_PRIVACY,
-
-	__HCI_CONN_NUM_FLAGS,
+	HCI_CONN_FLAG_REMOTE_WAKEUP = 1,
+	HCI_CONN_FLAG_DEVICE_PRIVACY = 2,
 };
-
-/* Make sure number of flags doesn't exceed sizeof(current_flags) */
-static_assert(__HCI_CONN_NUM_FLAGS < 32);
+typedef u8 hci_conn_flags_t;
 
 struct bdaddr_list_with_flags {
 	struct list_head list;
 	bdaddr_t bdaddr;
 	u8 bdaddr_type;
-	DECLARE_BITMAP(flags, __HCI_CONN_NUM_FLAGS);
+	hci_conn_flags_t flags;
 };
 
 struct bt_uuid {
@@ -576,7 +573,7 @@ struct hci_dev {
 	struct rfkill		*rfkill;
 
 	DECLARE_BITMAP(dev_flags, __HCI_NUM_FLAGS);
-	DECLARE_BITMAP(conn_flags, __HCI_CONN_NUM_FLAGS);
+	hci_conn_flags_t	conn_flags;
 
 	__s8			adv_tx_power;
 	__u8			adv_data[HCI_MAX_EXT_AD_LENGTH];
@@ -775,7 +772,7 @@ struct hci_conn_params {
 
 	struct hci_conn *conn;
 	bool explicit_connect;
-	DECLARE_BITMAP(flags, __HCI_CONN_NUM_FLAGS);
+	hci_conn_flags_t flags;
 	u8  privacy_mode;
 };