FAILED: patch "[PATCH] auxdisplay: charlcd: properly restore atomic counter on error" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Oct 10, 2017

Subsystems (3)

Stable branch Auxiliary display drivers Parallel LCD/keypad panel driver

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2017-10-10 15:03 UTC #0 lore raw

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 93dc1774d2a4c7a298d5cdf78cc8acdcb7b1428d Mon Sep 17 00:00:00 2001

From: Willy Tarreau <[email protected]>
Date: Thu, 7 Sep 2017 15:37:30 +0200
Subject: [PATCH] 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 [email protected]

Cc Mariusz Gorski <[email protected]>

Cc Geert Uytterhoeven <[email protected]>

Cc Miguel Ojeda Sandonis <[email protected]>

Signed-off-by Willy Tarreau <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

drivers/auxdisplay/charlcd.c +9 -2

index cfeb049a01ef..642afd88870b 100644
@@ -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)

drivers/auxdisplay/panel.c +9 -2

index df126dcdaf18..6911acd896d9 100644
@@ -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)