From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jiri Slaby <jirislaby@kernel.org>
Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>,
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: Sat, 27 Jun 2020 13:43:23 +0200 [thread overview]
Message-ID: <20200627114323.GA1645692@kroah.com> (raw)
In-Reply-To: <954840f0-2078-fe0f-1e52-d985a4997564@kernel.org>
On Wed, Jun 24, 2020 at 11:42:59AM +0200, Jiri Slaby wrote:
> 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.
Yeah, you are right, dropping them both now, thanks.
greg k-h
prev parent reply other threads:[~2020-06-27 11:43 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
2020-06-27 11:43 ` Greg Kroah-Hartman [this message]
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