This is a note to let you know that I've just added the patch titled
misc: panel: properly restore atomic counter on error path
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: misc-panel-properly-restore-atomic-counter-on-error-path.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 7ddfddb3fc0afb2aa36e89b554f06c901c5fa36f Mon Sep 17 00:00:00 2001
From: Willy Tarreau w@1wt.eu Date: Thu, 7 Sep 2017 11:56:40 +0200 Subject: 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 --- drivers/misc/panel.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-)
--- a/drivers/misc/panel.c +++ b/drivers/misc/panel.c @@ -1423,17 +1423,25 @@ static ssize_t lcd_write(struct file *fi
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 *
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)
Patches currently in stable-queue which might be from w@1wt.eu are
queue-4.9/misc-panel-properly-restore-atomic-counter-on-error-path.patch