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Commit e81b96ca authored by Willy Tarreau's avatar Willy Tarreau Committed by Greg Kroah-Hartman
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misc: panel: properly restore atomic counter on error path 



commit 93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d upstream.

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).

Fixes: f4757af8 # 3.19-rc1
Cc: Mariusz Gorski <marius.gorski@gmail.com>
Signed-off-by: default avatarWilly Tarreau <w@1wt.eu>
[wt: driver is in misc/panel in 4.9]
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b2dbcb7c

drivers/misc/panel.c

+19 −4
Original line number Diff line number Diff line
@@ -1423,17 +1423,25 @@ static ssize_t lcd_write(struct file *file, 


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

{

	int ret;



	ret = -EBUSY;

	if (!atomic_dec_and_test(&lcd_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 (lcd.must_clear) {

		lcd_clear_display();

		lcd.must_clear = false;

	}

	return nonseekable_open(inode, file);



 fail:

	atomic_inc(&lcd_available);

	return ret;

}



static int lcd_release(struct inode *inode, struct file *file)
@@ -1696,14 +1704,21 @@ 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)