forked from Minki/linux
02e246aee8
The L2CAP connection's channel list lock (conn->chan_lock) must never be taken while already holding a channel lock (chan->lock) in order to avoid lock-inversion and lockdep warnings. So far the l2cap_chan_connect function has acquired the chan->lock early in the function and then later called l2cap_chan_add(conn, chan) which will try to take the conn->chan_lock. This violates the correct order of taking the locks and may lead to the following type of lockdep warnings: -> #1 (&conn->chan_lock){+.+...}: [<c109324d>] lock_acquire+0x9d/0x140 [<c188459c>] mutex_lock_nested+0x6c/0x420 [<d0aab48e>] l2cap_chan_add+0x1e/0x40 [bluetooth] [<d0aac618>] l2cap_chan_connect+0x348/0x8f0 [bluetooth] [<d0cc9a91>] lowpan_control_write+0x221/0x2d0 [bluetooth_6lowpan] -> #0 (&chan->lock){+.+.+.}: [<c10928d8>] __lock_acquire+0x1a18/0x1d20 [<c109324d>] lock_acquire+0x9d/0x140 [<c188459c>] mutex_lock_nested+0x6c/0x420 [<d0ab05fd>] l2cap_connect_cfm+0x1dd/0x3f0 [bluetooth] [<d0a909c4>] hci_le_meta_evt+0x11a4/0x1260 [bluetooth] [<d0a910eb>] hci_event_packet+0x3ab/0x3120 [bluetooth] [<d0a7cb08>] hci_rx_work+0x208/0x4a0 [bluetooth] CPU0 CPU1 ---- ---- lock(&conn->chan_lock); lock(&chan->lock); lock(&conn->chan_lock); lock(&chan->lock); Before calling l2cap_chan_add() the channel is not part of the conn->chan_l list, and can therefore only be accessed by the L2CAP user (such as l2cap_sock.c). We can therefore assume that it is the responsibility of the user to handle mutual exclusion until this point (which we can see is already true in l2cap_sock.c by it in many places touching chan members without holding chan->lock). Since the hci_conn and by exctension l2cap_conn creation in the l2cap_chan_connect() function depend on chan details we cannot simply add a mutex_lock(&conn->chan_lock) in the beginning of the function (since the conn object doesn't yet exist there). What we can do however is move the chan->lock taking later into the function where we already have the conn object and can that way take conn->chan_lock first. This patch implements the above strategy and does some other necessary changes such as using __l2cap_chan_add() which assumes conn->chan_lock is held, as well as adding a second needed label so the unlocking happens as it should. Reported-by: Jukka Rissanen <jukka.rissanen@linux.intel.com> Signed-off-by: Johan Hedberg <johan.hedberg@intel.com> Tested-by: Jukka Rissanen <jukka.rissanen@linux.intel.com> Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com> Signed-off-by: Marcel Holtmann <marcel@holtmann.org> |
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| .. | ||
| bnep | ||
| cmtp | ||
| hidp | ||
| rfcomm | ||
| 6lowpan.c | ||
| a2mp.c | ||
| a2mp.h | ||
| af_bluetooth.c | ||
| amp.c | ||
| amp.h | ||
| hci_conn.c | ||
| hci_core.c | ||
| hci_event.c | ||
| hci_sock.c | ||
| hci_sysfs.c | ||
| Kconfig | ||
| l2cap_core.c | ||
| l2cap_sock.c | ||
| lib.c | ||
| Makefile | ||
| mgmt.c | ||
| sco.c | ||
| smp.c | ||
| smp.h | ||