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Subject[PATCH v2] drivers: tty: Merge alloc_tty_struct and initialize_tty_struct
Date
The two functions alloc_tty_struct and initialize_tty_struct are
always called together. Merge them into alloc_tty_struct, updating its
prototype and the only two callers of these functions.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
I hope this is sufficient. Thanks, Dan and Julia!

v2: Don't cause NULL pointer dereference or use-after-free on error
path. Just give module_put the same argument as was given to
try_module_get.

drivers/tty/pty.c | 21 ++++++++++-----------
drivers/tty/tty_io.c | 37 +++++++++++++------------------------
include/linux/tty.h | 4 +---
3 files changed, 24 insertions(+), 38 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 25c9bc7..9bbdb1d 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -316,7 +316,7 @@ done:
* pty_common_install - set up the pty pair
* @driver: the pty driver
* @tty: the tty being instantiated
- * @bool: legacy, true if this is BSD style
+ * @legacy: true if this is BSD style
*
* Perform the initial set up for the tty/pty pair. Called from the
* tty layer when the port is first opened.
@@ -331,18 +331,17 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
int idx = tty->index;
int retval = -ENOMEM;

- o_tty = alloc_tty_struct();
- if (!o_tty)
- goto err;
ports[0] = kmalloc(sizeof **ports, GFP_KERNEL);
ports[1] = kmalloc(sizeof **ports, GFP_KERNEL);
if (!ports[0] || !ports[1])
- goto err_free_tty;
+ goto err;
if (!try_module_get(driver->other->owner)) {
/* This cannot in fact currently happen */
- goto err_free_tty;
+ goto err;
}
- initialize_tty_struct(o_tty, driver->other, idx);
+ o_tty = alloc_tty_struct(driver->other, idx);
+ if (!o_tty)
+ goto err_put_module;

if (legacy) {
/* We always use new tty termios data so we can do this
@@ -387,12 +386,12 @@ err_free_termios:
tty_free_termios(tty);
err_deinit_tty:
deinitialize_tty_struct(o_tty);
- module_put(o_tty->driver->owner);
-err_free_tty:
- kfree(ports[0]);
- kfree(ports[1]);
free_tty_struct(o_tty);
+err_put_module:
+ module_put(driver->other->owner);
err:
+ kfree(ports[0]);
+ kfree(ports[1]);
return retval;
}

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 3411071..f63444d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -157,20 +157,6 @@ static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);

/**
- * alloc_tty_struct - allocate a tty object
- *
- * Return a new empty tty structure. The data fields have not
- * been initialized in any way but has been zeroed
- *
- * Locking: none
- */
-
-struct tty_struct *alloc_tty_struct(void)
-{
- return kzalloc(sizeof(struct tty_struct), GFP_KERNEL);
-}
-
-/**
* free_tty_struct - free a disused tty
* @tty: tty struct to free
*
@@ -1455,12 +1441,11 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx)
if (!try_module_get(driver->owner))
return ERR_PTR(-ENODEV);

- tty = alloc_tty_struct();
+ tty = alloc_tty_struct(driver, idx);
if (!tty) {
retval = -ENOMEM;
goto err_module_put;
}
- initialize_tty_struct(tty, driver, idx);

tty_lock(tty);
retval = tty_driver_install_tty(driver, tty);
@@ -3003,19 +2988,21 @@ static struct device *tty_get_device(struct tty_struct *tty)


/**
- * initialize_tty_struct
- * @tty: tty to initialize
+ * alloc_tty_struct
*
- * This subroutine initializes a tty structure that has been newly
- * allocated.
+ * This subroutine allocates and initializes a tty structure.
*
- * Locking: none - tty in question must not be exposed at this point
+ * Locking: none - tty in question is not exposed at this point
*/

-void initialize_tty_struct(struct tty_struct *tty,
- struct tty_driver *driver, int idx)
+struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
{
- memset(tty, 0, sizeof(struct tty_struct));
+ struct tty_struct *tty;
+
+ tty = kzalloc(sizeof(*tty), GFP_KERNEL);
+ if (!tty)
+ return NULL;
+
kref_init(&tty->kref);
tty->magic = TTY_MAGIC;
tty_ldisc_init(tty);
@@ -3039,6 +3026,8 @@ void initialize_tty_struct(struct tty_struct *tty,
tty->index = idx;
tty_line_name(driver, idx, tty->name);
tty->dev = tty_get_device(tty);
+
+ return tty;
}

/**
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 1c3316a..8413294 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -477,13 +477,11 @@ extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
unsigned int cmd, unsigned long arg);
extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);
extern void tty_default_fops(struct file_operations *fops);
-extern struct tty_struct *alloc_tty_struct(void);
+extern struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx);
extern int tty_alloc_file(struct file *file);
extern void tty_add_file(struct tty_struct *tty, struct file *file);
extern void tty_free_file(struct file *file);
extern void free_tty_struct(struct tty_struct *tty);
-extern void initialize_tty_struct(struct tty_struct *tty,
- struct tty_driver *driver, int idx);
extern void deinitialize_tty_struct(struct tty_struct *tty);
extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx);
extern int tty_release(struct inode *inode, struct file *filp);
--
1.9.2


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