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Subject[PATCH 07/24] Bluetooth: Release rfcomm_dev only once
Date
No logic prevents an rfcomm_dev from being released multiple
times. For example, if the rfcomm_dev ref count is large due
to pending tx, then multiple RFCOMMRELEASEDEV ioctls may
mistakenly release the rfcomm_dev too many times. Note that
concurrent ioctls are not required to create this condition.

Introduce RFCOMM_DEV_RELEASED status bit which guarantees the
rfcomm_dev can only be released once.

NB: Since the flags are exported to userspace, introduce the status
field to track state for which userspace should not be aware.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
include/net/bluetooth/rfcomm.h | 6 +++++-
net/bluetooth/rfcomm/tty.c | 11 +++++++++--
2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/net/bluetooth/rfcomm.h b/include/net/bluetooth/rfcomm.h
index 486213a..29d9727 100644
--- a/include/net/bluetooth/rfcomm.h
+++ b/include/net/bluetooth/rfcomm.h
@@ -323,11 +323,15 @@ int rfcomm_connect_ind(struct rfcomm_session *s, u8 channel,
#define RFCOMMGETDEVINFO _IOR('R', 211, int)
#define RFCOMMSTEALDLC _IOW('R', 220, int)

+/* rfcomm_dev.flags bit definitions */
#define RFCOMM_REUSE_DLC 0
#define RFCOMM_RELEASE_ONHUP 1
#define RFCOMM_HANGUP_NOW 2
#define RFCOMM_TTY_ATTACHED 3
-#define RFCOMM_TTY_RELEASED 4
+#define RFCOMM_DEFUNCT_BIT4 4 /* don't reuse this bit - userspace visible */
+
+/* rfcomm_dev.status bit definitions */
+#define RFCOMM_DEV_RELEASED 0

struct rfcomm_dev_req {
s16 dev_id;
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index b385d99..d9d4bc8 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -51,6 +51,8 @@ struct rfcomm_dev {
unsigned long flags;
int err;

+ unsigned long status; /* don't export to userspace */
+
bdaddr_t src;
bdaddr_t dst;
u8 channel;
@@ -423,6 +425,12 @@ static int rfcomm_release_dev(void __user *arg)
return -EPERM;
}

+ /* only release once */
+ if (test_and_set_bit(RFCOMM_DEV_RELEASED, &dev->status)) {
+ tty_port_put(&dev->port);
+ return -EALREADY;
+ }
+
if (req.flags & (1 << RFCOMM_HANGUP_NOW))
rfcomm_dlc_close(dev->dlc, 0);

@@ -433,8 +441,7 @@ static int rfcomm_release_dev(void __user *arg)
tty_kref_put(tty);
}

- if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) &&
- !test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
+ if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
tty_port_put(&dev->port);

tty_port_put(&dev->port);
--
1.8.1.2


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