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authorAlan Cox <alan@linux.intel.com>2012-05-29 13:45:01 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-29 10:42:13 -0700
commitd3ca8b64b97ef4dc54d7bb0b88bbc01a1fca8cb9 (patch)
tree6205c4d17144485ff6ec3783463b0ed6e84bf831 /drivers
parenta01ee165a132fadb57659d26246e340d6ac53265 (diff)
downloadlinux-d3ca8b64b97ef4dc54d7bb0b88bbc01a1fca8cb9.tar.bz2
pty: Fix lock inversion
The ptmx_open path takes the tty and devpts locks in the wrong order because tty_init_dev locks and returns a locked tty. As far as I can tell this is actually safe anyway because the tty being returned is new so nobody can get a reference to lock it at this point. However we don't even need the devpts lock at this point, it's only held as a byproduct of the way the locks were pushe down. Signed-off-by: Alan Cox <alan@linux.intel.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/tty/pty.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 59af3945ea85..65c7c62c7aae 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -633,7 +633,6 @@ static int ptmx_open(struct inode *inode, struct file *filp)
mutex_unlock(&devpts_mutex);
mutex_lock(&tty_mutex);
- mutex_lock(&devpts_mutex);
tty = tty_init_dev(ptm_driver, index);
if (IS_ERR(tty)) {
@@ -643,7 +642,6 @@ static int ptmx_open(struct inode *inode, struct file *filp)
/* The tty returned here is locked so we can safely
drop the mutex */
- mutex_unlock(&devpts_mutex);
mutex_unlock(&tty_mutex);
set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */