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authorJiri Slaby <jslaby@suse.cz>2011-08-10 14:59:28 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-08-23 10:10:38 -0700
commit24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24 (patch)
tree3dfb2053f7785508304fd29d6c1bb6e6a42a7d5c /drivers/tty/tty_io.c
parentdbb3b1ca5609d1f3848cd387d06cc60aaacf7f98 (diff)
downloadop-kernel-dev-24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24.zip
op-kernel-dev-24d406a6bf736f7aebdc8fa0f0ec86e0890c6d24.tar.gz
TTY: pty, fix pty counting
tty_operations->remove is normally called like: queue_release_one_tty ->tty_shutdown ->tty_driver_remove_tty ->tty_operations->remove However tty_shutdown() is called from queue_release_one_tty() only if tty_operations->shutdown is NULL. But for pty, it is not. pty_unix98_shutdown() is used there as ->shutdown. So tty_operations->remove of pty (i.e. pty_unix98_remove()) is never called. This results in invalid pty_count. I.e. what can be seen in /proc/sys/kernel/pty/nr. I see this was already reported at: https://lkml.org/lkml/2009/11/5/370 But it was not fixed since then. This patch is kind of a hackish way. The problem lies in ->install. We allocate there another tty (so-called tty->link). So ->install is called once, but ->remove twice, for both tty and tty->link. The fix here is to count both tty and tty->link and divide the count by 2 for user. And to have ->remove called, let's make tty_driver_remove_tty() global and call that from pty_unix98_shutdown() (tty_operations->shutdown). While at it, let's document that when ->shutdown is defined, tty_shutdown() is not called. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Alan Cox <alan@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/tty/tty_io.c')
-rw-r--r--drivers/tty/tty_io.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 150e4f7..4f1fc81 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1295,8 +1295,7 @@ static int tty_driver_install_tty(struct tty_driver *driver,
*
* Locking: tty_mutex for now
*/
-static void tty_driver_remove_tty(struct tty_driver *driver,
- struct tty_struct *tty)
+void tty_driver_remove_tty(struct tty_driver *driver, struct tty_struct *tty)
{
if (driver->ops->remove)
driver->ops->remove(driver, tty);
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