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SubjectRe: [043/127] TTY: ldisc, fix open flag handling
On 12/08/2010 04:02 PM, Greg KH wrote:
> On Wed, Dec 08, 2010 at 07:24:46AM +0100, Jiri Slaby wrote:
>> On 12/08/2010 01:43 AM, Greg KH wrote:
>>> 2.6.32-stable review patch. If anyone has any objections, please let us know.
>>>
>>> ------------------
>>>
>>> From: Jiri Slaby <jslaby@suse.cz>
>>>
>>> commit 7f90cfc505d613f4faf096e0d84ffe99208057d9 upstream.
>>>
>>> When a concrete ldisc open fails in tty_ldisc_open, we forget to clear
>>> TTY_LDISC_OPEN. This causes a false warning on the next ldisc open:
>>> WARNING: at drivers/char/tty_ldisc.c:445 tty_ldisc_open+0x26/0x38()
>>> Hardware name: System Product Name
>>> Modules linked in: ...
>>> Pid: 5251, comm: a.out Tainted: G W 2.6.32-5-686 #1
>>> Call Trace:
>>> [<c1030321>] ? warn_slowpath_common+0x5e/0x8a
>>> [<c1030357>] ? warn_slowpath_null+0xa/0xc
>>> [<c119311c>] ? tty_ldisc_open+0x26/0x38
>>> [<c11936c5>] ? tty_set_ldisc+0x218/0x304
>>> ...
>>>
>>> So clear the bit when failing...
>>>
>>> Introduced in c65c9bc3efa (tty: rewrite the ldisc locking) back in
>>> 2.6.31-rc1.
>>>
>>> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
>>> Cc: Alan Cox <alan@linux.intel.com>
>>> Reported-by: Sergey Lapin <slapin@ossfans.org>
>>> Tested-by: Sergey Lapin <slapin@ossfans.org>
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
>>>
>>> ---
>>> drivers/char/tty_ldisc.c | 9 +++++++--
>>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> --- a/drivers/char/tty_ldisc.c
>>> +++ b/drivers/char/tty_ldisc.c
>>> @@ -444,9 +444,14 @@ static void tty_set_termios_ldisc(struct
>>>
>>> static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
>>> {
>>> + int ret;
>>> +
>>> WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
>>> - if (ld->ops->open)
>>> - return ld->ops->open(tty);
>>> + if (ld->ops->open) {
>>> + ret = ld->ops->open(tty);
>>> + if (ret)
>>> + clear_bit(TTY_LDISC_OPEN, &tty->flags);
>>> + }
>>> return 0;
>>
>> Whoops, this should write return ret; (with int ret = 0;)
>>
>> Do you want me to send the patch against rebased on .32?
>
> No, send it based on Linus's tree as it's wrong there, right? Then it
> will move through to the stable kernels.

Nope, in 2.6.36 and newer it looks differently, only the .32 backport is
broken.

The .36 backport is OK:
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -454,6 +454,8 @@ static int tty_ldisc_open(struct tty_str
/* BTM here locks versus a hangup event */
WARN_ON(!tty_locked());
ret = ld->ops->open(tty);
+ if (ret)
+ clear_bit(TTY_LDISC_OPEN, &tty->flags);
return ret;
}
return 0;
thanks,
--
js
suse labs


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