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misc: panel: properly restore atomic counter on error path

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commit 93dc1774d2 upstream.

Commit f4757af ("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: f4757af85 # 3.19-rc1
Cc: Mariusz Gorski <marius.gorski@gmail.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
[wt: driver is in staging/panel in 4.4]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Willy Tarreau 2017-09-07 11:56:40 +02:00 committed by Greg Kroah-Hartman
parent 01000c56ca
commit e8d650563c
1 changed files with 21 additions and 6 deletions
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27
drivers/staging/panel/panel.c
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@ -1431,17 +1431,25 @@ static ssize_t lcd_write(struct file *file,
static int lcd_open(struct inode *inode, struct file *file)
{
if (!atomic_dec_and_test(&lcd_available))
return -EBUSY; /* open only once at a time */
int ret;
ret = -EBUSY;
if (!atomic_dec_and_test(&lcd_available))
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)
@ -1704,14 +1712,21 @@ static ssize_t keypad_read(struct file *file,
static int keypad_open(struct inode *inode, struct file *file)
{
if (!atomic_dec_and_test(&keypad_available))
return -EBUSY; /* open only once at a time */
int ret;
ret = -EBUSY;
if (!atomic_dec_and_test(&keypad_available))
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)