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authorArnd Bergmann <arnd@arndb.de>2010-06-01 22:53:02 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-10 13:47:43 -0700
commit64ba3dc3143d94bbe935722aa17fa516b232bc83 (patch)
tree9649ffd431eb8dc97fbad83d47feaed96980cb7e /drivers/char/pty.c
parentec79d6056de58511d8e46d9ae59d3878f958dc3e (diff)
tty: never hold BTM while getting tty_mutex
tty_mutex is never taken with the BTM held, except for two corner cases that are worked around here. We give up the BTM before calling tty_release() in the error path of tty_open(). Similarly, we reorder the locking in ptmx_open() to get tty_mutex before the BTM. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/char/pty.c')
-rw-r--r--drivers/char/pty.c24
1 files changed, 11 insertions, 13 deletions
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 622e21ca9a5..de22ea95283 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -647,7 +647,7 @@ static const struct tty_operations pty_unix98_ops = {
* allocated_ptys_lock handles the list of free pty numbers
*/
-static int __ptmx_open(struct inode *inode, struct file *filp)
+static int ptmx_open(struct inode *inode, struct file *filp)
{
struct tty_struct *tty;
int retval;
@@ -656,11 +656,14 @@ static int __ptmx_open(struct inode *inode, struct file *filp)
nonseekable_open(inode, filp);
/* find a device that is not in use. */
+ tty_lock();
index = devpts_new_index(inode);
+ tty_unlock();
if (index < 0)
return index;
mutex_lock(&tty_mutex);
+ tty_lock();
tty = tty_init_dev(ptm_driver, index, 1);
mutex_unlock(&tty_mutex);
@@ -678,24 +681,19 @@ static int __ptmx_open(struct inode *inode, struct file *filp)
goto out1;
retval = ptm_driver->ops->open(tty, filp);
- if (!retval)
- return 0;
+ if (retval)
+ goto out2;
out1:
+ tty_unlock();
+ return retval;
+out2:
+ tty_unlock();
tty_release(inode, filp);
return retval;
out:
devpts_kill_index(inode, index);
- return retval;
-}
-
-static int ptmx_open(struct inode *inode, struct file *filp)
-{
- int ret;
-
- tty_lock();
- ret = __ptmx_open(inode, filp);
tty_unlock();
- return ret;
+ return retval;
}
static struct file_operations ptmx_fops;