4.9-stable review patch. If anyone has any objections, please let me know.
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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)