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tty: hold lock across tty buffer finding and buffer filling 

tty_buffer_request_room is well protected, but while after it returns,
 it releases the port->lock. tty->buf.tail might be modified
by either irq handler or other threads. The patch adds more protection
by holding the lock across tty buffer finding and buffer filling.

Signed-off-by: Alek Du <alek.du@intel.com>
Signed-off-by: Xiaobing Tu <xiaobing.tu@intel.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Xiaobing Tu 2012-03-16 03:00:26 +00:00 committed by Greg Kroah-Hartman
parent 871bdea6f8
commit c56a00a165
1 changed files with 65 additions and 20 deletions
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85
drivers/tty/tty_buffer.c
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@ -185,25 +185,19 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
/* Should possibly check if this fails for the largest buffer we
have queued and recycle that ? */
}
/**
* tty_buffer_request_room - grow tty buffer if needed
* __tty_buffer_request_room - grow tty buffer if needed
* @tty: tty structure
* @size: size desired
*
* Make at least size bytes of linear space available for the tty
* buffer. If we fail return the size we managed to find.
*
* Locking: Takes tty->buf.lock
* Locking: Caller must hold tty->buf.lock
*/
int tty_buffer_request_room(struct tty_struct *tty, size_t size)
static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
{
struct tty_buffer *b, *n;
int left;
unsigned long flags;
spin_lock_irqsave(&tty->buf.lock, flags);
/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
remove this conditional if its worth it. This would be invisible
to the callers */
@ -225,9 +219,30 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
size = left;
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
return size;
}
/**
* tty_buffer_request_room - grow tty buffer if needed
* @tty: tty structure
* @size: size desired
*
* Make at least size bytes of linear space available for the tty
* buffer. If we fail return the size we managed to find.
*
* Locking: Takes tty->buf.lock
*/
int tty_buffer_request_room(struct tty_struct *tty, size_t size)
{
unsigned long flags;
int length;
spin_lock_irqsave(&tty->buf.lock, flags);
length = __tty_buffer_request_room(tty, size);
spin_unlock_irqrestore(&tty->buf.lock, flags);
return length;
}
EXPORT_SYMBOL_GPL(tty_buffer_request_room);
/**
@ -249,14 +264,22 @@ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
int copied = 0;
do {
int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
int space = tty_buffer_request_room(tty, goal);
struct tty_buffer *tb = tty->buf.tail;
int space;
unsigned long flags;
struct tty_buffer *tb;
spin_lock_irqsave(&tty->buf.lock, flags);
space = __tty_buffer_request_room(tty, goal);
tb = tty->buf.tail;
/* If there is no space then tb may be NULL */
if (unlikely(space == 0))
if (unlikely(space == 0)) {
spin_unlock_irqrestore(&tty->buf.lock, flags);
break;
}
memcpy(tb->char_buf_ptr + tb->used, chars, space);
memset(tb->flag_buf_ptr + tb->used, flag, space);
tb->used += space;
spin_unlock_irqrestore(&tty->buf.lock, flags);
copied += space;
chars += space;
/* There is a small chance that we need to split the data over
@ -286,14 +309,22 @@ int tty_insert_flip_string_flags(struct tty_struct *tty,
int copied = 0;
do {
int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
int space = tty_buffer_request_room(tty, goal);
struct tty_buffer *tb = tty->buf.tail;
int space;
unsigned long __flags;
struct tty_buffer *tb;
spin_lock_irqsave(&tty->buf.lock, __flags);
space = __tty_buffer_request_room(tty, goal);
tb = tty->buf.tail;
/* If there is no space then tb may be NULL */
if (unlikely(space == 0))
if (unlikely(space == 0)) {
spin_unlock_irqrestore(&tty->buf.lock, __flags);
break;
}
memcpy(tb->char_buf_ptr + tb->used, chars, space);
memcpy(tb->flag_buf_ptr + tb->used, flags, space);
tb->used += space;
spin_unlock_irqrestore(&tty->buf.lock, __flags);
copied += space;
chars += space;
flags += space;
@ -344,13 +375,20 @@ EXPORT_SYMBOL(tty_schedule_flip);
int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
size_t size)
{
int space = tty_buffer_request_room(tty, size);
int space;
unsigned long flags;
struct tty_buffer *tb;
spin_lock_irqsave(&tty->buf.lock, flags);
space = __tty_buffer_request_room(tty, size);
tb = tty->buf.tail;
if (likely(space)) {
struct tty_buffer *tb = tty->buf.tail;
*chars = tb->char_buf_ptr + tb->used;
memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
tb->used += space;
}
spin_unlock_irqrestore(&tty->buf.lock, flags);
return space;
}
EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
@ -374,13 +412,20 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
int tty_prepare_flip_string_flags(struct tty_struct *tty,
unsigned char **chars, char **flags, size_t size)
{
int space = tty_buffer_request_room(tty, size);
int space;
unsigned long __flags;
struct tty_buffer *tb;
spin_lock_irqsave(&tty->buf.lock, __flags);
space = __tty_buffer_request_room(tty, size);
tb = tty->buf.tail;
if (likely(space)) {
struct tty_buffer *tb = tty->buf.tail;
*chars = tb->char_buf_ptr + tb->used;
*flags = tb->flag_buf_ptr + tb->used;
tb->used += space;
}
spin_unlock_irqrestore(&tty->buf.lock, __flags);
return space;
}
EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);