FAILED: patch "[PATCH] PCI: endpoint: Avoid creating sub-groups asynchronously" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-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]>.

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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 7c5c7d06bd1f86d2c3ebe62be903a4ba42db4d2c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026021308-foil-sycamore-7994@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 7c5c7d06bd1f86d2c3ebe62be903a4ba42db4d2c Mon Sep 17 00:00:00 2001
From: Liu Song <[email protected]>
Date: Thu, 10 Jul 2025 14:38:45 +0800
Subject: [PATCH] PCI: endpoint: Avoid creating sub-groups asynchronously

The asynchronous creation of sub-groups by a delayed work could lead to a NULL pointer dereference when the driver directory is removed before the work completes.

The crash can be easily reproduced with the following commands:

  # cd /sys/kernel/config/pci_ep/functions/pci_epf_test
  # for i in {1..20}; do mkdir test && rmdir test; done

  BUG: kernel NULL pointer dereference, address: 0000000000000088
  ...
  Call Trace:
   configfs_register_group+0x3d/0x190
   pci_epf_cfs_work+0x41/0x110
   process_one_work+0x18f/0x350
   worker_thread+0x25a/0x3a0

Fix this issue by using configfs_add_default_group() API which does not have the deadlock problem as configfs_register_group() and does not require the delayed work handler.

index ef50c82e647f..43feb6139fa3 100644
@@ -23,7 +23,6 @@ struct pci_epf_group {
 	struct config_group group;
 	struct config_group primary_epc_group;
 	struct config_group secondary_epc_group;
-	struct delayed_work cfs_work;
 	struct pci_epf *epf;
 	int index;
 };

@@ -103,7 +102,7 @@ static struct config_group
 	secondary_epc_group = &epf_group->secondary_epc_group;
 	config_group_init_type_name(secondary_epc_group, "secondary",
 				    &pci_secondary_epc_type);
-	configfs_register_group(&epf_group->group, secondary_epc_group);
+	configfs_add_default_group(secondary_epc_group, &epf_group->group);
 
 	return secondary_epc_group;
 }

@@ -166,7 +165,7 @@ static struct config_group
 
 	config_group_init_type_name(primary_epc_group, "primary",
 				    &pci_primary_epc_type);
-	configfs_register_group(&epf_group->group, primary_epc_group);
+	configfs_add_default_group(primary_epc_group, &epf_group->group);
 
 	return primary_epc_group;
 }

@@ -570,15 +569,13 @@ static void pci_ep_cfs_add_type_group(struct pci_epf_group *epf_group)
 		return;
 	}
 
-	configfs_register_group(&epf_group->group, group);
+	configfs_add_default_group(group, &epf_group->group);
 }
 
-static void pci_epf_cfs_work(struct work_struct *work)
+static void pci_epf_cfs_add_sub_groups(struct pci_epf_group *epf_group)
 {
-	struct pci_epf_group *epf_group;
 	struct config_group *group;
 
-	epf_group = container_of(work, struct pci_epf_group, cfs_work.work);
 	group = pci_ep_cfs_add_primary_group(epf_group);
 	if (IS_ERR(group)) {
 		pr_err("failed to create 'primary' EPC interface\n");

@@ -637,9 +634,7 @@ static struct config_group *pci_epf_make(struct config_group *group,
 
 	kfree(epf_name);
 
-	INIT_DELAYED_WORK(&epf_group->cfs_work, pci_epf_cfs_work);
-	queue_delayed_work(system_wq, &epf_group->cfs_work,
-			   msecs_to_jiffies(1));
+	pci_epf_cfs_add_sub_groups(epf_group);
 
 	return &epf_group->group;
 

From: Damien Le Moal <[email protected]>

[ Upstream commit 70b3740f2c1941e2006d61539131b70d20cba9a6 ]

A PCI endpoint function driver can define function specific attributes under its function configfs directory using the add_cfs() endpoint driver operation. This is done by tying up the mkdir operation for the function configfs directory to a call to the add_cfs() operation. However, there are no checks preventing the user from repeatedly creating function specific attribute directories with different names, resulting in the same endpoint specific attributes group being added multiple times, which also result in an invalid reference counting for the attribute groups. E.g., using the pci-epf-ntb function driver as an example, the user creates the function as follows:

  $ modprobe pci-epf-ntb
  $ cd /sys/kernel/config/pci_ep/functions/pci_epf_ntb
  $ mkdir func0
  $ tree func0
  func0/
  |-- baseclass_code
  |-- cache_line_size
  |-- ...
  `-- vendorid

  $ mkdir func0/attrs
  $ tree func0
  func0/
  |-- attrs
  |   |-- db_count
  |   |-- mw1
  |   |-- mw2
  |   |-- mw3
  |   |-- mw4
  |   |-- num_mws
  |   `-- spad_count
  |-- baseclass_code
  |-- cache_line_size
  |-- ...
  `-- vendorid

At this point, the function can be started by linking the EP controller. However, if the user mistakenly creates again a directory:

  $ mkdir func0/attrs2
  $ tree func0
  func0/
  |-- attrs
  |   |-- db_count
  |   |-- mw1
  |   |-- mw2
  |   |-- mw3
  |   |-- mw4
  |   |-- num_mws
  |   `-- spad_count
  |-- attrs2
  |   |-- db_count
  |   |-- mw1
  |   |-- mw2
  |   |-- mw3
  |   |-- mw4
  |   |-- num_mws
  |   `-- spad_count
  |-- baseclass_code
  |-- cache_line_size
  |-- ...
  `-- vendorid

The endpoint function specific attributes are duplicated and cause a crash when the endpoint function device is torn down:

refcount_t: addition on 0; use-after-free.

  WARNING: CPU: 2 PID: 834 at lib/refcount.c:25 refcount_warn_saturate+0xc8/0x144
  CPU: 2 PID: 834 Comm: rmdir Not tainted 6.3.0-rc1 #1
  Hardware name: Pine64 RockPro64 v2.1 (DT)
  pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  ...
  Call trace:
  refcount_warn_saturate+0xc8/0x144
  config_item_get+0x7c/0x80
  configfs_rmdir+0x17c/0x30c
  vfs_rmdir+0x8c/0x204
  do_rmdir+0x158/0x184
  __arm64_sys_unlinkat+0x64/0x80
  invoke_syscall+0x48/0x114
  ...

Fix this by modifying pci_epf_cfs_work() to execute the new function pci_ep_cfs_add_type_group() which itself calls pci_epf_type_add_cfs() to obtain the function specific attribute group and the group name (directory name) from the endpoint function driver. If the function driver defines an attribute group, pci_ep_cfs_add_type_group() then proceeds to register this group using configfs_register_group(), thus automatically exposing the function type specific configfs attributes to the user. E.g.:

  $ modprobe pci-epf-ntb
  $ cd /sys/kernel/config/pci_ep/functions/pci_epf_ntb
  $ mkdir func0
  $ tree func0
  func0/
  |-- baseclass_code
  |-- cache_line_size
  |-- ...
  |-- pci_epf_ntb.0
  |   |-- db_count
  |   |-- mw1
  |   |-- mw2
  |   |-- mw3
  |   |-- mw4
  |   |-- num_mws
  |   `-- spad_count
  |-- primary
  |-- ...
  `-- vendorid

With this change, there is no need for the user to create or delete directories in the endpoint function attributes directory. The pci_epf_type_group_ops group operations are thus removed.

Also update the documentation for the pci-epf-ntb and pci-epf-vntb function drivers to reflect this change, removing the explanations showing the need to manually create the sub-directory for the function specific attributes.

Stable-dep-of: 7c5c7d06bd1f ("PCI: endpoint: Avoid creating sub-groups asynchronously")

---
 Documentation/PCI/endpoint/pci-ntb-howto.rst  | 11 ++---
 Documentation/PCI/endpoint/pci-vntb-howto.rst | 13 +++---
 drivers/pci/endpoint/pci-ep-cfs.c             | 42 +++++++++----------
 3 files changed, 29 insertions(+), 37 deletions(-)

index 1884bf29caba4..4261e7157ef1c 100644
@@ -88,13 +88,10 @@ commands can be used::
 	# echo 0x104c > functions/pci_epf_ntb/func1/vendorid
 	# echo 0xb00d > functions/pci_epf_ntb/func1/deviceid
 
-In order to configure NTB specific attributes, a new sub-directory to func1
-should be created::
-
-	# mkdir functions/pci_epf_ntb/func1/pci_epf_ntb.0/
-
-The NTB function driver will populate this directory with various attributes
-that can be configured by the user::
+The PCI endpoint framework also automatically creates a sub-directory in the
+function attribute directory. This sub-directory has the same name as the name
+of the function device and is populated with the following NTB specific
+attributes that can be configured by the user::
 
 	# ls functions/pci_epf_ntb/func1/pci_epf_ntb.0/
 	db_count    mw1         mw2         mw3         mw4         num_mws

index 4ab8e4a26d4be..70d3bc90893f3 100644
@@ -84,13 +84,10 @@ commands can be used::
 	# echo 0x1957 > functions/pci_epf_vntb/func1/vendorid
 	# echo 0x0809 > functions/pci_epf_vntb/func1/deviceid
 
-In order to configure NTB specific attributes, a new sub-directory to func1
-should be created::
-
-	# mkdir functions/pci_epf_vntb/func1/pci_epf_vntb.0/
-
-The NTB function driver will populate this directory with various attributes
-that can be configured by the user::
+The PCI endpoint framework also automatically creates a sub-directory in the
+function attribute directory. This sub-directory has the same name as the name
+of the function device and is populated with the following NTB specific
+attributes that can be configured by the user::
 
 	# ls functions/pci_epf_vntb/func1/pci_epf_vntb.0/
 	db_count    mw1         mw2         mw3         mw4         num_mws

@@ -103,7 +100,7 @@ A sample configuration for NTB function is given below::
 	# echo 1 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/num_mws
 	# echo 0x100000 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/mw1
 
-A sample configuration for virtual NTB driver for virutal PCI bus::
+A sample configuration for virtual NTB driver for virtual PCI bus::
 
 	# echo 0x1957 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_vid
 	# echo 0x080A > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_pid

2.51.0

From: Christophe JAILLET <[email protected]>

[ Upstream commit 328e4dffbeecc0f2cc5a149dee6c11a0577c9671 ]

In "struct pci_epf_group", the 'type_group' field is unused.

This was added, but already unused, by commit 70b3740f2c19 ("PCI: endpoint:
Automatically create a function specific attributes group").

Thus, remove it.

Found with cppcheck, unusedStructMember.

Stable-dep-of: 7c5c7d06bd1f ("PCI: endpoint: Avoid creating sub-groups asynchronously")

---
 drivers/pci/endpoint/pci-ep-cfs.c | 1 -
 1 file changed, 1 deletion(-)

index 76cffd1c18d8a..d8fe8a2d8e433 100644
@@ -23,7 +23,6 @@ struct pci_epf_group {
 	struct config_group group;
 	struct config_group primary_epc_group;
 	struct config_group secondary_epc_group;
-	struct config_group *type_group;
 	struct delayed_work cfs_work;
 	struct pci_epf *epf;
 	int index;

2.51.0

From: Liu Song <[email protected]>

[ Upstream commit 7c5c7d06bd1f86d2c3ebe62be903a4ba42db4d2c ]

The asynchronous creation of sub-groups by a delayed work could lead to a NULL pointer dereference when the driver directory is removed before the work completes.

The crash can be easily reproduced with the following commands:

  # cd /sys/kernel/config/pci_ep/functions/pci_epf_test
  # for i in {1..20}; do mkdir test && rmdir test; done

  BUG: kernel NULL pointer dereference, address: 0000000000000088
  ...
  Call Trace:
   configfs_register_group+0x3d/0x190
   pci_epf_cfs_work+0x41/0x110
   process_one_work+0x18f/0x350
   worker_thread+0x25a/0x3a0

Fix this issue by using configfs_add_default_group() API which does not have the deadlock problem as configfs_register_group() and does not require the delayed work handler.

---
 drivers/pci/endpoint/pci-ep-cfs.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

index d8fe8a2d8e433..9fb35cf023316 100644
@@ -23,7 +23,6 @@ struct pci_epf_group {
 	struct config_group group;
 	struct config_group primary_epc_group;
 	struct config_group secondary_epc_group;
-	struct delayed_work cfs_work;
 	struct pci_epf *epf;
 	int index;
 };

@@ -100,7 +99,7 @@ static struct config_group
 	secondary_epc_group = &epf_group->secondary_epc_group;
 	config_group_init_type_name(secondary_epc_group, "secondary",
 				    &pci_secondary_epc_type);
-	configfs_register_group(&epf_group->group, secondary_epc_group);
+	configfs_add_default_group(secondary_epc_group, &epf_group->group);
 
 	return secondary_epc_group;
 }

@@ -160,7 +159,7 @@ static struct config_group
 
 	config_group_init_type_name(primary_epc_group, "primary",
 				    &pci_primary_epc_type);
-	configfs_register_group(&epf_group->group, primary_epc_group);
+	configfs_add_default_group(primary_epc_group, &epf_group->group);
 
 	return primary_epc_group;
 }

@@ -522,15 +521,13 @@ static void pci_ep_cfs_add_type_group(struct pci_epf_group *epf_group)
 		return;
 	}
 
-	configfs_register_group(&epf_group->group, group);
+	configfs_add_default_group(group, &epf_group->group);
 }
 
-static void pci_epf_cfs_work(struct work_struct *work)
+static void pci_epf_cfs_add_sub_groups(struct pci_epf_group *epf_group)
 {
-	struct pci_epf_group *epf_group;
 	struct config_group *group;
 
-	epf_group = container_of(work, struct pci_epf_group, cfs_work.work);
 	group = pci_ep_cfs_add_primary_group(epf_group);
 	if (IS_ERR(group)) {
 		pr_err("failed to create 'primary' EPC interface\n");

@@ -589,9 +586,7 @@ static struct config_group *pci_epf_make(struct config_group *group,
 
 	kfree(epf_name);
 
-	INIT_DELAYED_WORK(&epf_group->cfs_work, pci_epf_cfs_work);
-	queue_delayed_work(system_wq, &epf_group->cfs_work,
-			   msecs_to_jiffies(1));
+	pci_epf_cfs_add_sub_groups(epf_group);
 
 	return &epf_group->group;
 

2.51.0