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n_gsm: added interlocking for gsm_data_lock for certain code paths

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There were some locking holes in the management of the MUX's
message queue for 2 code paths:
1) gsmld_write_wakeup
2) receipt of CMD_FCON flow-control message
In both cases gsm_data_kick is called w/o locking so it can collide
with other other instances of gsm_data_kick (pulling messages tx_tail)
or potentially other instances of __gsm_data_queu (adding messages to tx_head)

Changed to take the tx_lock in these 2 cases

Signed-off-by: Russ Gorby <russ.gorby@intel.com>
Tested-by: Yin, Fengwei <fengwei.yin@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Riding School <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Russ Gorby 2012-08-13 13:44:40 +01:00 committed by Greg Kroah-Hartman
parent 10c6c383e4
commit 5e44708f75
1 changed files with 6 additions and 2 deletions
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8
drivers/tty/n_gsm.c
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@ -1205,6 +1205,8 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
u8 *data, int clen)
{
u8 buf[1];
unsigned long flags;
switch (command) {
case CMD_CLD: {
struct gsm_dlci *dlci = gsm->dlci[0];
@ -1225,7 +1227,9 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
gsm->constipated = 0;
gsm_control_reply(gsm, CMD_FCON, NULL, 0);
/* Kick the link in case it is idling */
spin_lock_irqsave(&gsm->tx_lock, flags);
gsm_data_kick(gsm);
spin_unlock_irqrestore(&gsm->tx_lock, flags);
break;
case CMD_FCOFF:
/* Modem wants us to STFU */
@ -2392,12 +2396,12 @@ static void gsmld_write_wakeup(struct tty_struct *tty)
/* Queue poll */
clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
spin_lock_irqsave(&gsm->tx_lock, flags);
gsm_data_kick(gsm);
if (gsm->tx_bytes < TX_THRESH_LO) {
spin_lock_irqsave(&gsm->tx_lock, flags);
gsm_dlci_data_sweep(gsm);
spin_unlock_irqrestore(&gsm->tx_lock, flags);
}
spin_unlock_irqrestore(&gsm->tx_lock, flags);
}
/**