From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: [PATCH 6/8] n_gsm: avoid accessing freed memory during CMD_FCOFF condition Date: Mon, 13 Aug 2012 13:44:59 +0100 Message-ID: <20120813124451.6125.35751.stgit@localhost.localdomain> References: <20120813124254.6125.70371.stgit@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:43386 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751665Ab2HMM1i (ORCPT ); Mon, 13 Aug 2012 08:27:38 -0400 In-Reply-To: <20120813124254.6125.70371.stgit@localhost.localdomain> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: greg@kroah.com, linux-serial@vger.kernel.org From: Russ Gorby gsm_data_kick was recently modified to allow messages on the tx queue bound for DLCI0 to flow even during FCOFF conditions. Unfortunately we introduced a bug discovered by code inspection where subsequent list traversers can access freed memory if the DLCI0 messages were not all at the head of the list. Replaced singly linked tx list w/ a list_head and used provided interfaces for traversing and deleting members. Signed-off-by: Russ Gorby Tested-by: Yin, Fengwei Signed-off-by: Alan Cox Cc: Riding School --- drivers/tty/n_gsm.c | 40 +++++++++++++--------------------------- 1 file changed, 13 insertions(+), 27 deletions(-) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 51ba2f2..e2bdb8b 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -108,7 +108,7 @@ struct gsm_mux_net { */ struct gsm_msg { - struct gsm_msg *next; + struct list_head list; u8 addr; /* DLCI address + flags */ u8 ctrl; /* Control byte + flags */ unsigned int len; /* Length of data block (can be zero) */ @@ -245,8 +245,7 @@ struct gsm_mux { unsigned int tx_bytes; /* TX data outstanding */ #define TX_THRESH_HI 8192 #define TX_THRESH_LO 2048 - struct gsm_msg *tx_head; /* Pending data packets */ - struct gsm_msg *tx_tail; + struct list_head tx_list; /* Pending data packets */ /* Control messages */ struct timer_list t2_timer; /* Retransmit timer for commands */ @@ -663,7 +662,7 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len, m->len = len; m->addr = addr; m->ctrl = ctrl; - m->next = NULL; + INIT_LIST_HEAD(&m->list); return m; } @@ -681,16 +680,13 @@ static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len, static void gsm_data_kick(struct gsm_mux *gsm) { - struct gsm_msg *msg = gsm->tx_head; - struct gsm_msg *free_msg; + struct gsm_msg *msg, *nmsg; int len; int skip_sof = 0; - while (msg) { - if (gsm->constipated && msg->addr) { - msg = msg->next; + list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) { + if (gsm->constipated && msg->addr) continue; - } if (gsm->encoding != 0) { gsm->txframe[0] = GSM1_SOF; len = gsm_stuff_frame(msg->data, @@ -718,14 +714,9 @@ static void gsm_data_kick(struct gsm_mux *gsm) burst */ skip_sof = 1; - if (gsm->tx_head == msg) - gsm->tx_head = msg->next; - free_msg = msg; - msg = msg->next; - kfree(free_msg); + list_del(&msg->list); + kfree(msg); } - if (!gsm->tx_head) - gsm->tx_tail = NULL; } /** @@ -774,11 +765,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) msg->data = dp; /* Add to the actual output queue */ - if (gsm->tx_tail) - gsm->tx_tail->next = msg; - else - gsm->tx_head = msg; - gsm->tx_tail = msg; + list_add_tail(&msg->list, &gsm->tx_list); gsm->tx_bytes += msg->len; gsm_data_kick(gsm); } @@ -2026,7 +2013,7 @@ void gsm_cleanup_mux(struct gsm_mux *gsm) { int i; struct gsm_dlci *dlci = gsm->dlci[0]; - struct gsm_msg *txq; + struct gsm_msg *txq, *utxq; struct gsm_control *gc; gsm->dead = 1; @@ -2061,11 +2048,9 @@ void gsm_cleanup_mux(struct gsm_mux *gsm) if (gsm->dlci[i]) gsm_dlci_release(gsm->dlci[i]); /* Now wipe the queues */ - for (txq = gsm->tx_head; txq != NULL; txq = gsm->tx_head) { - gsm->tx_head = txq->next; + list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list) kfree(txq); - } - gsm->tx_tail = NULL; + INIT_LIST_HEAD(&gsm->tx_list); } EXPORT_SYMBOL_GPL(gsm_cleanup_mux); @@ -2176,6 +2161,7 @@ struct gsm_mux *gsm_alloc_mux(void) } spin_lock_init(&gsm->lock); kref_init(&gsm->ref); + INIT_LIST_HEAD(&gsm->tx_list); gsm->t1 = T1; gsm->t2 = T2;