diff options
| author | Willy Tarreau <w@1wt.eu> | 2017-09-07 11:56:40 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-11-18 11:22:25 +0100 |
| commit | e81b96cab11f57506ade92656a76db8bbe7b6673 (patch) | |
| tree | 7e2411f0a8f8b2f0d4c37241b3453041f81cf860 | |
| parent | b2dbcb7c969dcb6a2dcbe901a4a9070bb30e4788 (diff) | |
misc: panel: properly restore atomic counter on error path
commit 93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d 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 misc/panel in 4.9]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/misc/panel.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/drivers/misc/panel.c b/drivers/misc/panel.c index 6030ac5b8c63..a9fa4c0ac220 100644 --- a/drivers/misc/panel.c +++ b/drivers/misc/panel.c @@ -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) |