Re: Serial buffer memory leak

[Paul Fulghum <paulkf@microgate.com>]

Laurent Pinchart wrote:
> Patch c5c34d4862e18ef07c1276d233507f540fb5a532 (tty: flush flip buffer on 
> ldisc input queue flush) introduces a race condition which can lead to memory 
> leaks.
>
> The problem can be triggered when tcflush() is called when data are being 
> pushed to the line discipline driver by flush_to_ldisc().
>
> flush_to_ldisc() releases tty->buf.lock when calling the line discipline 
> receive_buf function. At that poing tty_buffer_flush() kicks in and sets both 
> tty->buf.head and tty->buf.tail to NULL. When flush_to_ldisc() finishes, it 
> restores tty->buf.head but doesn't touch tty->buf.tail. This corrups the 
> buffer queue, and the next call to tty_buffer_request_room() will allocate a 
> new buffer and overwrite tty->buf.head. The previous buffer is then lost 
> forever without being released.

Your description is clear enough, I'll make the patch.

Thanks,
Paul
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