Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 93dc1774 authored by Willy Tarreau's avatar Willy Tarreau Committed by Greg Kroah-Hartman
Browse files

auxdisplay: charlcd: properly restore atomic counter on error path 



Commit f4757af8 ("staging: panel: Fix single-open policy race condition")
introduced in 3.19-rc1 attempted to fix a race condition on the open, but
failed to properly do it and used to exit without restoring the semaphore.

This results in -EBUSY being returned after the first open error until
the module is reloaded or the system restarted (ie: consecutive to a
dual open resulting in -EBUSY or to a permission error).

[ Note for stable maintainers: the code moved from drivers/misc/panel.c
  to drivers/auxdisplay/{charlcd,panel}.c during 4.12. The patch easily
  applies there (modulo the renamed atomic counter) but I can provide a
  tested backport if desired. ]

Fixes: f4757af8 # 3.19-rc1
Cc: stable@vger.kernel.org
Cc: Mariusz Gorski <marius.gorski@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d53bebdf

drivers/auxdisplay/charlcd.c

+9 −2
Original line number Diff line number Diff line
@@ -647,18 +647,25 @@ static ssize_t charlcd_write(struct file *file, const char __user *buf, 
static int charlcd_open(struct inode *inode, struct file *file)

{

	struct charlcd_priv *priv = to_priv(the_charlcd);

	int ret;



	ret = -EBUSY;

	if (!atomic_dec_and_test(&charlcd_available))

		return -EBUSY;	/* open only once at a time */

		goto fail;	/* open only once at a time */



	ret = -EPERM;

	if (file->f_mode & FMODE_READ)	/* device is write-only */

		return -EPERM;

		goto fail;



	if (priv->must_clear) {

		charlcd_clear_display(&priv->lcd);

		priv->must_clear = false;

	}

	return nonseekable_open(inode, file);



 fail:

	atomic_inc(&charlcd_available);

	return ret;

}



static int charlcd_release(struct inode *inode, struct file *file)

drivers/auxdisplay/panel.c

+9 −2
Original line number Diff line number Diff line
@@ -1105,14 +1105,21 @@ static ssize_t keypad_read(struct file *file, 


static int keypad_open(struct inode *inode, struct file *file)

{

	int ret;



	ret = -EBUSY;

	if (!atomic_dec_and_test(&keypad_available))

		return -EBUSY;	/* open only once at a time */

		goto fail;	/* open only once at a time */



	ret = -EPERM;

	if (file->f_mode & FMODE_WRITE)	/* device is read-only */

		return -EPERM;

		goto fail;



	keypad_buflen = 0;	/* flush the buffer on opening */

	return 0;

 fail:

	atomic_inc(&keypad_available);

	return ret;

}



static int keypad_release(struct inode *inode, struct file *file)