diff options
Diffstat (limited to 'kernels/linux-libre-nand/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch')
| -rw-r--r-- | kernels/linux-libre-nand/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/kernels/linux-libre-nand/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch b/kernels/linux-libre-nand/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch new file mode 100644 index 000000000..0c13c9867 --- /dev/null +++ b/kernels/linux-libre-nand/0001-tty-n_hdlc-get-rid-of-racy-n_hdlc_tbuf.patch @@ -0,0 +1,311 @@ +>From 1dea7a8061ad9212f4464464a80d0dcd477eceab Mon Sep 17 00:00:00 2001 +From: Alexander Popov <alex.popov () linux com> +Date: Tue, 28 Feb 2017 19:28:54 +0300 +Subject: [PATCH 1/1] tty: n_hdlc: get rid of racy n_hdlc.tbuf + +Currently N_HDLC line discipline uses a self-made singly linked list for +data buffers and has n_hdlc.tbuf pointer for buffer retransmitting after +an error. + +The commit be10eb7589337e5defbe214dae038a53dd21add8 +("tty: n_hdlc add buffer flushing") introduced racy access to n_hdlc.tbuf. +After tx error concurrent flush_tx_queue() and n_hdlc_send_frames() can put +one data buffer to tx_free_buf_list twice. That causes double free in +n_hdlc_release(). + +Let's use standard kernel linked list and get rid of n_hdlc.tbuf: +in case of tx error put current data buffer after the head of tx_buf_list. + +Signed-off-by: Alexander Popov <alex.popov () linux com> +--- + drivers/tty/n_hdlc.c | 132 +++++++++++++++++++++++++++------------------------ + 1 file changed, 69 insertions(+), 63 deletions(-) + +diff --git a/drivers/tty/n_hdlc.c b/drivers/tty/n_hdlc.c +index eb27883..728c824 100644 +--- a/drivers/tty/n_hdlc.c ++++ b/drivers/tty/n_hdlc.c +@@ -114,7 +114,7 @@ + #define DEFAULT_TX_BUF_COUNT 3 + + struct n_hdlc_buf { +- struct n_hdlc_buf *link; ++ struct list_head list_item; + int count; + char buf[1]; + }; +@@ -122,8 +122,7 @@ struct n_hdlc_buf { + #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe) + + struct n_hdlc_buf_list { +- struct n_hdlc_buf *head; +- struct n_hdlc_buf *tail; ++ struct list_head list; + int count; + spinlock_t spinlock; + }; +@@ -136,7 +135,6 @@ struct n_hdlc_buf_list { + * @backup_tty - TTY to use if tty gets closed + * @tbusy - reentrancy flag for tx wakeup code + * @woke_up - FIXME: describe this field +- * @tbuf - currently transmitting tx buffer + * @tx_buf_list - list of pending transmit frame buffers + * @rx_buf_list - list of received frame buffers + * @tx_free_buf_list - list unused transmit frame buffers +@@ -149,7 +147,6 @@ struct n_hdlc { + struct tty_struct *backup_tty; + int tbusy; + int woke_up; +- struct n_hdlc_buf *tbuf; + struct n_hdlc_buf_list tx_buf_list; + struct n_hdlc_buf_list rx_buf_list; + struct n_hdlc_buf_list tx_free_buf_list; +@@ -159,6 +156,8 @@ struct n_hdlc { + /* + * HDLC buffer list manipulation functions + */ ++static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, ++ struct n_hdlc_buf *buf); + static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, + struct n_hdlc_buf *buf); + static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list); +@@ -208,16 +207,9 @@ static void flush_tx_queue(struct tty_struct *tty) + { + struct n_hdlc *n_hdlc = tty2n_hdlc(tty); + struct n_hdlc_buf *buf; +- unsigned long flags; + + while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list))) + n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf); +- spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags); +- if (n_hdlc->tbuf) { +- n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf); +- n_hdlc->tbuf = NULL; +- } +- spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); + } + + static struct tty_ldisc_ops n_hdlc_ldisc = { +@@ -283,7 +275,6 @@ static void n_hdlc_release(struct n_hdlc *n_hdlc) + } else + break; + } +- kfree(n_hdlc->tbuf); + kfree(n_hdlc); + + } /* end of n_hdlc_release() */ +@@ -402,13 +393,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) + n_hdlc->woke_up = 0; + spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); + +- /* get current transmit buffer or get new transmit */ +- /* buffer from list of pending transmit buffers */ +- +- tbuf = n_hdlc->tbuf; +- if (!tbuf) +- tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); +- ++ tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list); + while (tbuf) { + if (debuglevel >= DEBUG_LEVEL_INFO) + printk("%s(%d)sending frame %p, count=%d\n", +@@ -420,7 +405,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) + + /* rollback was possible and has been done */ + if (actual == -ERESTARTSYS) { +- n_hdlc->tbuf = tbuf; ++ n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); + break; + } + /* if transmit error, throw frame away by */ +@@ -435,10 +420,7 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) + + /* free current transmit buffer */ + n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf); +- +- /* this tx buffer is done */ +- n_hdlc->tbuf = NULL; +- ++ + /* wait up sleeping writers */ + wake_up_interruptible(&tty->write_wait); + +@@ -448,10 +430,12 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty) + if (debuglevel >= DEBUG_LEVEL_INFO) + printk("%s(%d)frame %p pending\n", + __FILE__,__LINE__,tbuf); +- +- /* buffer not accepted by driver */ +- /* set this buffer as pending buffer */ +- n_hdlc->tbuf = tbuf; ++ ++ /* ++ * the buffer was not accepted by driver, ++ * return it back into tx queue ++ */ ++ n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf); + break; + } + } +@@ -749,7 +733,8 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, + int error = 0; + int count; + unsigned long flags; +- ++ struct n_hdlc_buf *buf = NULL; ++ + if (debuglevel >= DEBUG_LEVEL_INFO) + printk("%s(%d)n_hdlc_tty_ioctl() called %d\n", + __FILE__,__LINE__,cmd); +@@ -763,8 +748,10 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, + /* report count of read data available */ + /* in next available frame (if any) */ + spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags); +- if (n_hdlc->rx_buf_list.head) +- count = n_hdlc->rx_buf_list.head->count; ++ buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list, ++ struct n_hdlc_buf, list_item); ++ if (buf) ++ count = buf->count; + else + count = 0; + spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags); +@@ -776,8 +763,10 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file, + count = tty_chars_in_buffer(tty); + /* add size of next output frame in queue */ + spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags); +- if (n_hdlc->tx_buf_list.head) +- count += n_hdlc->tx_buf_list.head->count; ++ buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list, ++ struct n_hdlc_buf, list_item); ++ if (buf) ++ count += buf->count; + spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags); + error = put_user(count, (int __user *)arg); + break; +@@ -825,14 +814,14 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, + poll_wait(filp, &tty->write_wait, wait); + + /* set bits for operations that won't block */ +- if (n_hdlc->rx_buf_list.head) ++ if (!list_empty(&n_hdlc->rx_buf_list.list)) + mask |= POLLIN | POLLRDNORM; /* readable */ + if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) + mask |= POLLHUP; + if (tty_hung_up_p(filp)) + mask |= POLLHUP; + if (!tty_is_writelocked(tty) && +- n_hdlc->tx_free_buf_list.head) ++ !list_empty(&n_hdlc->tx_free_buf_list.list)) + mask |= POLLOUT | POLLWRNORM; /* writable */ + } + return mask; +@@ -856,7 +845,12 @@ static struct n_hdlc *n_hdlc_alloc(void) + spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock); + spin_lock_init(&n_hdlc->rx_buf_list.spinlock); + spin_lock_init(&n_hdlc->tx_buf_list.spinlock); +- ++ ++ INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list); ++ INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list); ++ INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list); ++ INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list); ++ + /* allocate free rx buffer list */ + for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) { + buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL); +@@ -884,53 +878,65 @@ static struct n_hdlc *n_hdlc_alloc(void) + } /* end of n_hdlc_alloc() */ + + /** ++ * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list ++ * @buf_list - pointer to the buffer list ++ * @buf - pointer to the buffer ++ */ ++static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list, ++ struct n_hdlc_buf *buf) ++{ ++ unsigned long flags; ++ ++ spin_lock_irqsave(&buf_list->spinlock, flags); ++ ++ list_add(&buf->list_item, &buf_list->list); ++ buf_list->count++; ++ ++ spin_unlock_irqrestore(&buf_list->spinlock, flags); ++} ++ ++/** + * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list +- * @list - pointer to buffer list ++ * @buf_list - pointer to buffer list + * @buf - pointer to buffer + */ +-static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, ++static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list, + struct n_hdlc_buf *buf) + { + unsigned long flags; +- spin_lock_irqsave(&list->spinlock,flags); +- +- buf->link=NULL; +- if (list->tail) +- list->tail->link = buf; +- else +- list->head = buf; +- list->tail = buf; +- (list->count)++; +- +- spin_unlock_irqrestore(&list->spinlock,flags); +- ++ ++ spin_lock_irqsave(&buf_list->spinlock, flags); ++ ++ list_add_tail(&buf->list_item, &buf_list->list); ++ buf_list->count++; ++ ++ spin_unlock_irqrestore(&buf_list->spinlock, flags); + } /* end of n_hdlc_buf_put() */ + + /** + * n_hdlc_buf_get - remove and return an HDLC buffer from list +- * @list - pointer to HDLC buffer list ++ * @buf_list - pointer to HDLC buffer list + * + * Remove and return an HDLC buffer from the head of the specified HDLC buffer + * list. + * Returns a pointer to HDLC buffer if available, otherwise %NULL. + */ +-static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list) ++static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list) + { + unsigned long flags; + struct n_hdlc_buf *buf; +- spin_lock_irqsave(&list->spinlock,flags); +- +- buf = list->head; ++ ++ spin_lock_irqsave(&buf_list->spinlock, flags); ++ ++ buf = list_first_entry_or_null(&buf_list->list, ++ struct n_hdlc_buf, list_item); + if (buf) { +- list->head = buf->link; +- (list->count)--; ++ list_del(&buf->list_item); ++ buf_list->count--; + } +- if (!list->head) +- list->tail = NULL; +- +- spin_unlock_irqrestore(&list->spinlock,flags); ++ ++ spin_unlock_irqrestore(&buf_list->spinlock, flags); + return buf; +- + } /* end of n_hdlc_buf_get() */ + + static char hdlc_banner[] __initdata = +-- +2.7.4 + |