From: Jiri Slaby <jirislaby@kernel.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
yuanxzhang@fudan.edu.cn, kjlu@umn.edu,
Xin Tan <tanxin.ctf@gmail.com>
Subject: Re: [PATCH] tty: serial_core: Fix uart_state refcnt leak when the port startup
Date: Wed, 24 Jun 2020 11:42:59 +0200 [thread overview]
Message-ID: <954840f0-2078-fe0f-1e52-d985a4997564@kernel.org> (raw)
In-Reply-To: <20200624093407.GB1751086@kroah.com>
On 24. 06. 20, 11:34, Greg Kroah-Hartman wrote:
> On Sat, Jun 13, 2020 at 08:52:18PM +0800, Xiyu Yang wrote:
>> uart_port_startup() invokes uart_port_lock(), which returns a reference
>> of the uart_port object if increases the refcount of the uart_state
>> object successfully or returns NULL if fails.
>>
>> However, uart_port_startup() don't take the return value of
>> uart_port_lock() as the new uart_port object to "uport" and use the old
>> "uport" instead to balance refcount in uart_port_unlock(), which may
>> cause a redundant decrement of refcount occurred when the new "uport"
>> equals to NULL and then cause a potential memory leak.
>>
>> Fix this issue by update the "uport" object to the return value of
>> uart_port_lock() when invoking uart_port_lock().
>>
>> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
>> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
>> ---
>> drivers/tty/serial/serial_core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index 57840cf90388..968fd619aec0 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -205,7 +205,7 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
>> if (!page)
>> return -ENOMEM;
>>
>> - uart_port_lock(state, flags);
>> + uport = uart_port_lock(state, flags);
>
> How is this a different pointer than you originally had?
Was this patch sent twice? As I had very same questions on the other
one, but never received a feedback:
https://lore.kernel.org/linux-serial/bf6c1e7b-3dc6-aba6-955a-fee351a6d800@suse.com/
Oh, wait: this is uart_port_startup, I commented on the uart_shutdown
one. But whatever, I would scratch both of them.
> And if it is a different pointer, shouldn't you be calling this function
> and using the pointer much earlier in the function instead of just here?
>
> Can you trigger a problem that this patch solves? If so, how?
thanks,
--
js
suse labs
next prev parent reply other threads:[~2020-06-24 9:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-13 12:52 [PATCH] tty: serial_core: Fix uart_state refcnt leak when the port startup Xiyu Yang
2020-06-24 9:34 ` Greg Kroah-Hartman
2020-06-24 9:42 ` Jiri Slaby [this message]
2020-06-27 11:43 ` Greg Kroah-Hartman
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