diff options
| author | Willy Tarreau <w@1wt.eu> | 2017-09-07 15:37:30 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-09-18 16:06:00 +0200 |
| commit | 93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d (patch) | |
| tree | 32e7bcd21dfd863d3005e730ded8f1123519faf7 /drivers | |
| parent | d53bebdf4d779497b29e1aad26e19cac1d446f42 (diff) | |
| download | linux-93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d.tar.bz2 | |
auxdisplay: charlcd: properly restore atomic counter on error path
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).
[ 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: f4757af85 # 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: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/auxdisplay/charlcd.c | 11 | ||||
| -rw-r--r-- | drivers/auxdisplay/panel.c | 11 |
2 files changed, 18 insertions, 4 deletions
diff --git a/drivers/auxdisplay/charlcd.c b/drivers/auxdisplay/charlcd.c index cfeb049a01ef..642afd88870b 100644 --- a/drivers/auxdisplay/charlcd.c +++ b/drivers/auxdisplay/charlcd.c @@ -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) diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c index df126dcdaf18..6911acd896d9 100644 --- a/drivers/auxdisplay/panel.c +++ b/drivers/auxdisplay/panel.c @@ -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) |