Messages in this thread |  | | | Date | Fri, 16 Mar 2012 21:53:47 +0100 | | From | Jiri Slaby <> | | Subject | Re: [PATCH] tty: hold lock across tty buffer finding and buffer filling |
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On 03/16/2012 02:50 PM, Du, Alek wrote: > For #1, as I said, we already held the tty refcount. The tty refcount cannot help this crash.
Where exactly? Do you have some local changes? $ grep tty_port_tty_ drivers/tty/serial/mfd.c $
> For #2, this patch will avoid memcpy to a NULL pointer and avoid a kernel crash.
Ok, could you explain how? Linearized code from moxa.c with your patch applied follows: ofs = baseAddr + DynPage_addr + bufhead + head; size = (tail >= head) ? (tail - head) : (rx_mask + 1 - head); size = min(size, count); // call to tty_prepare_flip_string spin_lock_irqsave(&tty->buf.lock, flags); space = __tty_buffer_request_room(tty, size);
tb = tty->buf.tail; if (likely(space)) { *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 to MoxaPortReadData memcpy_fromio(*chars, ofs, space); <- memcpy without buf.lock head = (head + len) & rx_mask; ... thanks, -- js suse labs
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