[PATCH v2 3/3] mISDN: cache stable device names outside the kobject

From: Shuvam Pandey

Date: Fri Apr 17 2026 - 13:53:01 EST

mISDN prints and exports device names from several paths that are not tied
to the kobject rename internals. device_rename() replaces the kobject name
string, so reading it directly leaves mISDN dependent on that storage
remaining stable while those paths run.

Keep an mISDN-owned copy of the device name, update it on registration and
successful rename, and use that cached name from the socket, sysfs, stack,
and debug paths.

Assisted-by: Codex:GPT-5.3-Codex
Signed-off-by: Shuvam Pandey <shuvampandey1@xxxxxxxxx>
---
drivers/isdn/mISDN/core.c | 18 +++++++++++++-----
drivers/isdn/mISDN/layer1.c | 2 +-
drivers/isdn/mISDN/socket.c | 12 ++++++++----
drivers/isdn/mISDN/stack.c | 36 ++++++++++++++++++------------------
drivers/isdn/mISDN/tei.c | 2 +-
include/linux/mISDNif.h | 1 +
6 files changed, 42 insertions(+), 29 deletions(-)

diff --git a/drivers/isdn/mISDN/core.c b/drivers/isdn/mISDN/core.c
index 4e2be8f03119b..d89c9e54cb5fa 100644
--- a/drivers/isdn/mISDN/core.c
+++ b/drivers/isdn/mISDN/core.c
@@ -89,8 +89,15 @@ static DEVICE_ATTR_RO(protocol);
static ssize_t name_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- strcpy(buf, dev_name(dev));
- return strlen(buf);
+ struct mISDNdevice *mdev = dev_to_mISDN(dev);
+ ssize_t len;
+
+ if (!mdev)
+ return -ENODEV;
+ device_lock(dev);
+ len = sysfs_emit(buf, "%s", mdev->name);
+ device_unlock(dev);
+ return len;
}
static DEVICE_ATTR_RO(name);

@@ -227,9 +234,10 @@ mISDN_register_device(struct mISDNdevice *dev,
dev_set_name(&dev->dev, "%s", name);
else
dev_set_name(&dev->dev, "mISDN%d", dev->id);
+ strscpy(dev->name, dev_name(&dev->dev), sizeof(dev->name));
if (debug & DEBUG_CORE)
printk(KERN_DEBUG "mISDN_register %s %d\n",
- dev_name(&dev->dev), dev->id);
+ dev->name, dev->id);
dev->dev.class = &mISDN_class;

err = create_stack(dev);
@@ -258,7 +266,7 @@ void
mISDN_unregister_device(struct mISDNdevice *dev) {
if (debug & DEBUG_CORE)
printk(KERN_DEBUG "mISDN_unregister %s %d\n",
- dev_name(&dev->dev), dev->id);
+ dev->name, dev->id);
/* sysfs_remove_link(&dev->dev.kobj, "device"); */
/*
* Remove the device from sysfs before taking dev->mutex so bind-side
@@ -358,7 +366,7 @@ const char *mISDNDevName4ch(struct mISDNchannel *ch)
return msg_no_stack;
if (!ch->st->dev)
return msg_no_stackdev;
- return dev_name(&ch->st->dev->dev);
+ return ch->st->dev->name;
};
EXPORT_SYMBOL(mISDNDevName4ch);

diff --git a/drivers/isdn/mISDN/layer1.c b/drivers/isdn/mISDN/layer1.c
index 3fbc170acf9ab..c5a2e9119e868 100644
--- a/drivers/isdn/mISDN/layer1.c
+++ b/drivers/isdn/mISDN/layer1.c
@@ -100,7 +100,7 @@ l1m_debug(struct FsmInst *fi, char *fmt, ...)
vaf.fmt = fmt;
vaf.va = &va;

- printk(KERN_DEBUG "%s: %pV\n", dev_name(&l1->dch->dev.dev), &vaf);
+ printk(KERN_DEBUG "%s: %pV\n", l1->dch->dev.name, &vaf);

va_end(va);
}
diff --git a/drivers/isdn/mISDN/socket.c b/drivers/isdn/mISDN/socket.c
index 42cda5b8bbe16..bce71ae5eb7d4 100644
--- a/drivers/isdn/mISDN/socket.c
+++ b/drivers/isdn/mISDN/socket.c
@@ -499,7 +499,7 @@ data_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
memcpy(di.channelmap, dev->channelmap,
sizeof(di.channelmap));
di.nrbchan = dev->nrbchan;
- strscpy(di.name, dev_name(&dev->dev), sizeof(di.name));
+ strscpy(di.name, dev->name, sizeof(di.name));
device_unlock(&dev->dev);
if (copy_to_user((void __user *)arg, &di, sizeof(di)))
err = -EFAULT;
@@ -826,7 +826,7 @@ base_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
memcpy(di.channelmap, dev->channelmap,
sizeof(di.channelmap));
di.nrbchan = dev->nrbchan;
- strscpy(di.name, dev_name(&dev->dev), sizeof(di.name));
+ strscpy(di.name, dev->name, sizeof(di.name));
device_unlock(&dev->dev);
if (copy_to_user((void __user *)arg, &di, sizeof(di)))
err = -EFAULT;
@@ -846,10 +846,14 @@ base_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
dev = get_mdevice(dn.id);
if (dev) {
device_lock(&dev->dev);
- if (!device_is_registered(&dev->dev))
+ if (!device_is_registered(&dev->dev)) {
err = -ENODEV;
- else
+ } else {
err = device_rename(&dev->dev, dn.name);
+ if (!err)
+ strscpy(dev->name, dev_name(&dev->dev),
+ sizeof(dev->name));
+ }
device_unlock(&dev->dev);
put_device(&dev->dev);
} else {
diff --git a/drivers/isdn/mISDN/stack.c b/drivers/isdn/mISDN/stack.c
index 4e96684af0aac..9b39ddb4a0944 100644
--- a/drivers/isdn/mISDN/stack.c
+++ b/drivers/isdn/mISDN/stack.c
@@ -165,7 +165,7 @@ send_msg_to_layer(struct mISDNstack *st, struct sk_buff *skb)
else
printk(KERN_WARNING
"%s: dev(%s) prim(%x) id(%x) no channel\n",
- __func__, dev_name(&st->dev->dev), hh->prim,
+ __func__, st->dev->name, hh->prim,
hh->id);
} else if (lm == 0x8) {
WARN_ON(lm == 0x8);
@@ -175,12 +175,12 @@ send_msg_to_layer(struct mISDNstack *st, struct sk_buff *skb)
else
printk(KERN_WARNING
"%s: dev(%s) prim(%x) id(%x) no channel\n",
- __func__, dev_name(&st->dev->dev), hh->prim,
+ __func__, st->dev->name, hh->prim,
hh->id);
} else {
/* broadcast not handled yet */
printk(KERN_WARNING "%s: dev(%s) prim %x not delivered\n",
- __func__, dev_name(&st->dev->dev), hh->prim);
+ __func__, st->dev->name, hh->prim);
}
return -ESRCH;
}
@@ -202,7 +202,7 @@ mISDNStackd(void *data)
sigfillset(&current->blocked);
if (*debug & DEBUG_MSG_THREAD)
printk(KERN_DEBUG "mISDNStackd %s started\n",
- dev_name(&st->dev->dev));
+ st->dev->name);

if (st->notify != NULL) {
complete(st->notify);
@@ -238,7 +238,7 @@ mISDNStackd(void *data)
printk(KERN_DEBUG
"%s: %s prim(%x) id(%x) "
"send call(%d)\n",
- __func__, dev_name(&st->dev->dev),
+ __func__, st->dev->name,
mISDN_HEAD_PRIM(skb),
mISDN_HEAD_ID(skb), err);
dev_kfree_skb(skb);
@@ -281,7 +281,7 @@ mISDNStackd(void *data)
mISDN_STACK_ACTION_MASK));
if (*debug & DEBUG_MSG_THREAD)
printk(KERN_DEBUG "%s: %s wake status %08lx\n",
- __func__, dev_name(&st->dev->dev), st->status);
+ __func__, st->dev->name, st->status);
test_and_set_bit(mISDN_STACK_ACTIVE, &st->status);

test_and_clear_bit(mISDN_STACK_WAKEUP, &st->status);
@@ -296,17 +296,17 @@ mISDNStackd(void *data)
#ifdef MISDN_MSG_STATS
printk(KERN_DEBUG "mISDNStackd daemon for %s proceed %d "
"msg %d sleep %d stopped\n",
- dev_name(&st->dev->dev), st->msg_cnt, st->sleep_cnt,
+ st->dev->name, st->msg_cnt, st->sleep_cnt,
st->stopped_cnt);
task_cputime(st->thread, &utime, &stime);
printk(KERN_DEBUG
"mISDNStackd daemon for %s utime(%llu) stime(%llu)\n",
- dev_name(&st->dev->dev), utime, stime);
+ st->dev->name, utime, stime);
printk(KERN_DEBUG
"mISDNStackd daemon for %s nvcsw(%ld) nivcsw(%ld)\n",
- dev_name(&st->dev->dev), st->thread->nvcsw, st->thread->nivcsw);
+ st->dev->name, st->thread->nvcsw, st->thread->nivcsw);
printk(KERN_DEBUG "mISDNStackd daemon for %s killed now\n",
- dev_name(&st->dev->dev));
+ st->dev->name);
#endif
test_and_set_bit(mISDN_STACK_KILLED, &st->status);
test_and_clear_bit(mISDN_STACK_RUNNING, &st->status);
@@ -397,15 +397,15 @@ create_stack(struct mISDNdevice *dev)
newst->own.recv = mISDN_queue_message;
if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: st(%s)\n", __func__,
- dev_name(&newst->dev->dev));
+ newst->dev->name);
newst->notify = &done;
newst->thread = kthread_run(mISDNStackd, (void *)newst, "mISDN_%s",
- dev_name(&newst->dev->dev));
+ newst->dev->name);
if (IS_ERR(newst->thread)) {
err = PTR_ERR(newst->thread);
printk(KERN_ERR
"mISDN:cannot create kernel thread for %s (%d)\n",
- dev_name(&newst->dev->dev), err);
+ newst->dev->name, err);
delete_teimanager(dev->teimgr);
kfree(newst);
} else
@@ -424,7 +424,7 @@ connect_layer1(struct mISDNdevice *dev, struct mISDNchannel *ch,

if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: %s proto(%x) adr(%d %d %d %d)\n",
- __func__, dev_name(&dev->dev), protocol, adr->dev,
+ __func__, dev->name, protocol, adr->dev,
adr->channel, adr->sapi, adr->tei);
switch (protocol) {
case ISDN_P_NT_S0:
@@ -461,7 +461,7 @@ connect_Bstack(struct mISDNdevice *dev, struct mISDNchannel *ch,

if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: %s proto(%x) adr(%d %d %d %d)\n",
- __func__, dev_name(&dev->dev), protocol,
+ __func__, dev->name, protocol,
adr->dev, adr->channel, adr->sapi,
adr->tei);
ch->st = dev->D.st;
@@ -517,7 +517,7 @@ create_l2entity(struct mISDNdevice *dev, struct mISDNchannel *ch,

if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: %s proto(%x) adr(%d %d %d %d)\n",
- __func__, dev_name(&dev->dev), protocol,
+ __func__, dev->name, protocol,
adr->dev, adr->channel, adr->sapi,
adr->tei);
rq.protocol = ISDN_P_TE_S0;
@@ -570,7 +570,7 @@ delete_channel(struct mISDNchannel *ch)
}
if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: st(%s) protocol(%x)\n", __func__,
- dev_name(&ch->st->dev->dev), ch->protocol);
+ ch->st->dev->name, ch->protocol);
if (ch->protocol >= ISDN_P_B_START) {
if (ch->peer) {
ch->peer->ctrl(ch->peer, CLOSE_CHANNEL, NULL);
@@ -623,7 +623,7 @@ delete_stack(struct mISDNdevice *dev)

if (*debug & DEBUG_CORE_FUNC)
printk(KERN_DEBUG "%s: st(%s)\n", __func__,
- dev_name(&st->dev->dev));
+ st->dev->name);
if (dev->teimgr)
delete_teimanager(dev->teimgr);
if (st->thread) {
diff --git a/drivers/isdn/mISDN/tei.c b/drivers/isdn/mISDN/tei.c
index 2bad3083be901..876c1194920ef 100644
--- a/drivers/isdn/mISDN/tei.c
+++ b/drivers/isdn/mISDN/tei.c
@@ -990,7 +990,7 @@ create_teimgr(struct manager *mgr, struct channel_req *crq)

if (*debug & DEBUG_L2_TEI)
printk(KERN_DEBUG "%s: %s proto(%x) adr(%d %d %d %d)\n",
- __func__, dev_name(&mgr->ch.st->dev->dev),
+ __func__, mgr->ch.st->dev->name,
crq->protocol, crq->adr.dev, crq->adr.channel,
crq->adr.sapi, crq->adr.tei);
if (crq->adr.tei > GROUP_TEI)
diff --git a/include/linux/mISDNif.h b/include/linux/mISDNif.h
index ce26d70c1ebfb..79f6d8f218b13 100644
--- a/include/linux/mISDNif.h
+++ b/include/linux/mISDNif.h
@@ -497,6 +497,7 @@ struct mISDNdevice {
u_int Bprotocols;
u_int nrbchan;
u_char channelmap[MISDN_CHMAP_SIZE];
+ char name[MISDN_MAX_IDLEN];
struct list_head bchannels;
struct mISDNchannel *teimgr;
struct completion released;
--
2.50.1 (Apple Git-155)