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Commit 5e44708f authored by Russ Gorby's avatar Russ Gorby Committed by Greg Kroah-Hartman
Browse files

n_gsm: added interlocking for gsm_data_lock for certain code paths 



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: default avatarRuss Gorby <russ.gorby@intel.com>
Tested-by: default avatarYin, Fengwei <fengwei.yin@intel.com>
Signed-off-by: default avatarAlan Cox <alan@linux.intel.com>
Cc: Riding School <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 10c6c383

drivers/tty/n_gsm.c

+6 −2
Original line number Diff line number Diff line
@@ -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);

}



/**