FAILED: patch "[PATCH] usb: gadget: f_printer: take kref only for successful open" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] usb: gadget: f_printer: take kref only for successful open" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 30adce93d5c4a5a1ec29d9249e3fdfcc391d406b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071412-palpable-underuse-1c58@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 30adce93d5c4a5a1ec29d9249e3fdfcc391d406b Mon Sep 17 00:00:00 2001
From: Xu Rao <raoxu@uniontech.com>
Date: Fri, 26 Jun 2026 14:46:17 +0800
Subject: [PATCH] usb: gadget: f_printer: take kref only for successful open

printer_open() returns -EBUSY when the character device is already
open, but it increments dev->kref regardless of the return value. VFS
does not call ->release() for a failed open, so every rejected second
open permanently leaks one reference.

Move kref_get() into the successful-open branch.

Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire")
Cc: stable <stable@kernel.org>
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Link: https://patch.msgid.link/80295742B820DA9B+20260626064617.4090626-1-raoxu@uniontech.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index e4f7828ae75d..837f753d0cae 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -363,12 +363,11 @@ printer_open(struct inode *inode, struct file *fd)
 		ret = 0;
 		/* Change the printer status to show that it's on-line. */
 		dev->printer_status |= PRINTER_SELECTED;
+		kref_get(&dev->kref);
 	}
 
 	spin_unlock_irqrestore(&dev->lock, flags);
 
-	kref_get(&dev->kref);
-
 	return ret;
 }
 

[PATCH 5.15.y 1/2] usb: gadget: function: Simplify diagnostic messaging in printer

[Sasha Levin]

From: Andrzej Pietrasiewicz <andrzej.p@collabora.com>

[ Upstream commit 57b7b733b1a7aeab25bc2670afff608214284863 ]

Don't issue messages which can be easily achieved with ftrace.
In case of printer_open() the return code is propagated to other layers
so the user will know about -EBUSY anyway.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Link: https://lore.kernel.org/r/20221123110746.59611-1-andrzej.p@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 30adce93d5c4 ("usb: gadget: f_printer: take kref only for successful open")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/gadget/function/f_printer.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 728cb9702d5a99..60e833bd75f8e6 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -365,7 +365,7 @@ printer_open(struct inode *inode, struct file *fd)
 	spin_unlock_irqrestore(&dev->lock, flags);
 
 	kref_get(&dev->kref);
-	DBG(dev, "printer_open returned %x\n", ret);
+
 	return ret;
 }
 
@@ -383,7 +383,6 @@ printer_close(struct inode *inode, struct file *fd)
 	spin_unlock_irqrestore(&dev->lock, flags);
 
 	kref_put(&dev->kref, printer_dev_free);
-	DBG(dev, "printer_close\n");
 
 	return 0;
 }
@@ -868,8 +867,6 @@ static void printer_reset_interface(struct printer_dev *dev)
 	if (dev->interface < 0)
 		return;
 
-	DBG(dev, "%s\n", __func__);
-
 	if (dev->in_ep->desc)
 		usb_ep_disable(dev->in_ep);
 
@@ -907,8 +904,6 @@ static void printer_soft_reset(struct printer_dev *dev)
 {
 	struct usb_request	*req;
 
-	INFO(dev, "Received Printer Reset Request\n");
-
 	if (usb_ep_disable(dev->in_ep))
 		DBG(dev, "Failed to disable USB in_ep\n");
 	if (usb_ep_disable(dev->out_ep))
@@ -1205,8 +1200,6 @@ static void printer_func_disable(struct usb_function *f)
 {
 	struct printer_dev *dev = func_to_printer(f);
 
-	DBG(dev, "%s\n", __func__);
-
 	printer_reset_interface(dev);
 }
 
-- 
2.53.0

[PATCH 5.15.y 2/2] usb: gadget: f_printer: take kref only for successful open

[Sasha Levin]

From: Xu Rao <raoxu@uniontech.com>

[ Upstream commit 30adce93d5c4a5a1ec29d9249e3fdfcc391d406b ]

printer_open() returns -EBUSY when the character device is already
open, but it increments dev->kref regardless of the return value. VFS
does not call ->release() for a failed open, so every rejected second
open permanently leaks one reference.

Move kref_get() into the successful-open branch.

Fixes: e8d5f92b8d30 ("usb: gadget: function: printer: fix use-after-free in __lock_acquire")
Cc: stable <stable@kernel.org>
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Link: https://patch.msgid.link/80295742B820DA9B+20260626064617.4090626-1-raoxu@uniontech.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/gadget/function/f_printer.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 60e833bd75f8e6..4b107c26e0d7eb 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -360,12 +360,11 @@ printer_open(struct inode *inode, struct file *fd)
 		ret = 0;
 		/* Change the printer status to show that it's on-line. */
 		dev->printer_status |= PRINTER_SELECTED;
+		kref_get(&dev->kref);
 	}
 
 	spin_unlock_irqrestore(&dev->lock, flags);
 
-	kref_get(&dev->kref);
-
 	return ret;
 }
 
-- 
2.53.0