[PATCH net v3 0/3] vsock: Fix transport_{h2g,g2h,dgram,local} TOCTOU issues

[PATCH net v3 0/3] vsock: Fix transport_{h2g,g2h,dgram,local} TOCTOU issues

[Michal Luczaj]

transport_{h2g,g2h,dgram,local} may become NULL on vsock_core_unregister().
Make sure a poorly timed `rmmod transport` won't lead to a NULL/stale
pointer dereference.

Note that these oopses are pretty unlikely to happen in the wild. Splats
were collected after sprinkling kernel with mdelay()s.

Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
Changes in v3:
- Static transport_* CID getter rename and comment [Stefano]
- Link to v2: https://lore.kernel.org/r/20250620-vsock-transports-toctou-v2-0-02ebd20b1d03@rbox.co

Changes in v2:
- Introduce a helper function to get local CIDs safely [Stefano]
- Rename goto label to indicate an error path, explain why releasing
  vsock_register_mutex after try_module_get() is safe [Stefano]
- Link to v1: https://lore.kernel.org/r/20250618-vsock-transports-toctou-v1-0-dd2d2ede9052@rbox.co

---
Michal Luczaj (3):
      vsock: Fix transport_{g2h,h2g} TOCTOU
      vsock: Fix transport_* TOCTOU
      vsock: Fix IOCTL_VM_SOCKETS_GET_LOCAL_CID to check also `transport_local`

 net/vmw_vsock/af_vsock.c | 57 ++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 46 insertions(+), 11 deletions(-)
---
base-commit: 561aa0e22b70a5e7246b73d62a824b3aef3fc375
change-id: 20250523-vsock-transports-toctou-4b75d9c2a805

Best regards,
-- 
Michal Luczaj <mhal@rbox.co>

[PATCH net v3 1/3] vsock: Fix transport_{g2h,h2g} TOCTOU

[Michal Luczaj]

vsock_find_cid() and vsock_dev_do_ioctl() may race with module unload.
transport_{g2h,h2g} may become NULL after the NULL check.

Introduce vsock_transport_local_cid() to protect from a potential
null-ptr-deref.

KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
RIP: 0010:vsock_find_cid+0x47/0x90
Call Trace:
 __vsock_bind+0x4b2/0x720
 vsock_bind+0x90/0xe0
 __sys_bind+0x14d/0x1e0
 __x64_sys_bind+0x6e/0xc0
 do_syscall_64+0x92/0x1c0
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
RIP: 0010:vsock_dev_do_ioctl.isra.0+0x58/0xf0
Call Trace:
 __x64_sys_ioctl+0x12d/0x190
 do_syscall_64+0x92/0x1c0
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
 net/vmw_vsock/af_vsock.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 2e7a3034e965db30b6ee295370d866e6d8b1c341..39473b9e0829f240045262aef00cbae82a425dcc 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -531,9 +531,25 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 }
 EXPORT_SYMBOL_GPL(vsock_assign_transport);
 
+/*
+ * Provide safe access to static transport_{h2g,g2h,dgram,local} callbacks.
+ * Otherwise we may race with module removal. Do not use on `vsk->transport`.
+ */
+static u32 vsock_registered_transport_cid(const struct vsock_transport **transport)
+{
+	u32 cid = VMADDR_CID_ANY;
+
+	mutex_lock(&vsock_register_mutex);
+	if (*transport)
+		cid = (*transport)->get_local_cid();
+	mutex_unlock(&vsock_register_mutex);
+
+	return cid;
+}
+
 bool vsock_find_cid(unsigned int cid)
 {
-	if (transport_g2h && cid == transport_g2h->get_local_cid())
+	if (cid == vsock_registered_transport_cid(&transport_g2h))
 		return true;
 
 	if (transport_h2g && cid == VMADDR_CID_HOST)
@@ -2536,18 +2552,17 @@ static long vsock_dev_do_ioctl(struct file *filp,
 			       unsigned int cmd, void __user *ptr)
 {
 	u32 __user *p = ptr;
-	u32 cid = VMADDR_CID_ANY;
 	int retval = 0;
+	u32 cid;
 
 	switch (cmd) {
 	case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
 		/* To be compatible with the VMCI behavior, we prioritize the
 		 * guest CID instead of well-know host CID (VMADDR_CID_HOST).
 		 */
-		if (transport_g2h)
-			cid = transport_g2h->get_local_cid();
-		else if (transport_h2g)
-			cid = transport_h2g->get_local_cid();
+		cid = vsock_registered_transport_cid(&transport_g2h);
+		if (cid == VMADDR_CID_ANY)
+			cid = vsock_registered_transport_cid(&transport_h2g);
 
 		if (put_user(cid, p) != 0)
 			retval = -EFAULT;

-- 
2.49.0

[PATCH net v3 2/3] vsock: Fix transport_* TOCTOU

[Michal Luczaj]

Transport assignment may race with module unload. Protect new_transport
from becoming a stale pointer.

This also takes care of an insecure call in vsock_use_local_transport();
add a lockdep assert.

BUG: unable to handle page fault for address: fffffbfff8056000
Oops: Oops: 0000 [#1] SMP KASAN
RIP: 0010:vsock_assign_transport+0x366/0x600
Call Trace:
 vsock_connect+0x59c/0xc40
 __sys_connect+0xe8/0x100
 __x64_sys_connect+0x6e/0xc0
 do_syscall_64+0x92/0x1c0
 entry_SYSCALL_64_after_hwframe+0x4b/0x53

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
 net/vmw_vsock/af_vsock.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 39473b9e0829f240045262aef00cbae82a425dcc..9b2af5c63f7c2ae575c160415bd77208a3980835 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -407,6 +407,8 @@ EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
 
 static bool vsock_use_local_transport(unsigned int remote_cid)
 {
+	lockdep_assert_held(&vsock_register_mutex);
+
 	if (!transport_local)
 		return false;
 
@@ -464,6 +466,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 
 	remote_flags = vsk->remote_addr.svm_flags;
 
+	mutex_lock(&vsock_register_mutex);
+
 	switch (sk->sk_type) {
 	case SOCK_DGRAM:
 		new_transport = transport_dgram;
@@ -479,12 +483,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 			new_transport = transport_h2g;
 		break;
 	default:
-		return -ESOCKTNOSUPPORT;
+		ret = -ESOCKTNOSUPPORT;
+		goto err;
 	}
 
 	if (vsk->transport) {
-		if (vsk->transport == new_transport)
-			return 0;
+		if (vsk->transport == new_transport) {
+			ret = 0;
+			goto err;
+		}
 
 		/* transport->release() must be called with sock lock acquired.
 		 * This path can only be taken during vsock_connect(), where we
@@ -508,8 +515,16 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 	/* We increase the module refcnt to prevent the transport unloading
 	 * while there are open sockets assigned to it.
 	 */
-	if (!new_transport || !try_module_get(new_transport->module))
-		return -ENODEV;
+	if (!new_transport || !try_module_get(new_transport->module)) {
+		ret = -ENODEV;
+		goto err;
+	}
+
+	/* It's safe to release the mutex after a successful try_module_get().
+	 * Whichever transport `new_transport` points at, it won't go await
+	 * until the last module_put() below or in vsock_deassign_transport().
+	 */
+	mutex_unlock(&vsock_register_mutex);
 
 	if (sk->sk_type == SOCK_SEQPACKET) {
 		if (!new_transport->seqpacket_allow ||
@@ -528,6 +543,9 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
 	vsk->transport = new_transport;
 
 	return 0;
+err:
+	mutex_unlock(&vsock_register_mutex);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(vsock_assign_transport);
 

-- 
2.49.0

[PATCH net v3 3/3] vsock: Fix IOCTL_VM_SOCKETS_GET_LOCAL_CID to check also `transport_local`

[Michal Luczaj]

Support returning VMADDR_CID_LOCAL in case no other vsock transport is
available.

Fixes: 0e12190578d0 ("vsock: add local transport support in the vsock core")
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
---
 net/vmw_vsock/af_vsock.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 9b2af5c63f7c2ae575c160415bd77208a3980835..c8398f9cec5296e07395df8e7ad0f52b8ceb65d5 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -2581,6 +2581,8 @@ static long vsock_dev_do_ioctl(struct file *filp,
 		cid = vsock_registered_transport_cid(&transport_g2h);
 		if (cid == VMADDR_CID_ANY)
 			cid = vsock_registered_transport_cid(&transport_h2g);
+		if (cid == VMADDR_CID_ANY)
+			cid = vsock_registered_transport_cid(&transport_local);
 
 		if (put_user(cid, p) != 0)
 			retval = -EFAULT;

-- 
2.49.0

Re: [PATCH net v3 1/3] vsock: Fix transport_{g2h,h2g} TOCTOU

[Stefano Garzarella]

On Wed, Jul 02, 2025 at 03:38:43PM +0200, Michal Luczaj wrote:
>vsock_find_cid() and vsock_dev_do_ioctl() may race with module unload.
>transport_{g2h,h2g} may become NULL after the NULL check.
>
>Introduce vsock_transport_local_cid() to protect from a potential
>null-ptr-deref.
>
>KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
>RIP: 0010:vsock_find_cid+0x47/0x90
>Call Trace:
> __vsock_bind+0x4b2/0x720
> vsock_bind+0x90/0xe0
> __sys_bind+0x14d/0x1e0
> __x64_sys_bind+0x6e/0xc0
> do_syscall_64+0x92/0x1c0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
>
>KASAN: null-ptr-deref in range [0x0000000000000118-0x000000000000011f]
>RIP: 0010:vsock_dev_do_ioctl.isra.0+0x58/0xf0
>Call Trace:
> __x64_sys_ioctl+0x12d/0x190
> do_syscall_64+0x92/0x1c0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
>
>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> net/vmw_vsock/af_vsock.c | 27 +++++++++++++++++++++------
> 1 file changed, 21 insertions(+), 6 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Thanks!
Stefano

>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 2e7a3034e965db30b6ee295370d866e6d8b1c341..39473b9e0829f240045262aef00cbae82a425dcc 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -531,9 +531,25 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> }
> EXPORT_SYMBOL_GPL(vsock_assign_transport);
>
>+/*
>+ * Provide safe access to static transport_{h2g,g2h,dgram,local} callbacks.
>+ * Otherwise we may race with module removal. Do not use on `vsk->transport`.
>+ */
>+static u32 vsock_registered_transport_cid(const struct vsock_transport **transport)
>+{
>+	u32 cid = VMADDR_CID_ANY;
>+
>+	mutex_lock(&vsock_register_mutex);
>+	if (*transport)
>+		cid = (*transport)->get_local_cid();
>+	mutex_unlock(&vsock_register_mutex);
>+
>+	return cid;
>+}
>+
> bool vsock_find_cid(unsigned int cid)
> {
>-	if (transport_g2h && cid == transport_g2h->get_local_cid())
>+	if (cid == vsock_registered_transport_cid(&transport_g2h))
> 		return true;
>
> 	if (transport_h2g && cid == VMADDR_CID_HOST)
>@@ -2536,18 +2552,17 @@ static long vsock_dev_do_ioctl(struct file *filp,
> 			       unsigned int cmd, void __user *ptr)
> {
> 	u32 __user *p = ptr;
>-	u32 cid = VMADDR_CID_ANY;
> 	int retval = 0;
>+	u32 cid;
>
> 	switch (cmd) {
> 	case IOCTL_VM_SOCKETS_GET_LOCAL_CID:
> 		/* To be compatible with the VMCI behavior, we prioritize the
> 		 * guest CID instead of well-know host CID (VMADDR_CID_HOST).
> 		 */
>-		if (transport_g2h)
>-			cid = transport_g2h->get_local_cid();
>-		else if (transport_h2g)
>-			cid = transport_h2g->get_local_cid();
>+		cid = vsock_registered_transport_cid(&transport_g2h);
>+		if (cid == VMADDR_CID_ANY)
>+			cid = vsock_registered_transport_cid(&transport_h2g);
>
> 		if (put_user(cid, p) != 0)
> 			retval = -EFAULT;
>
>-- 
>2.49.0
>

Re: [PATCH net v3 2/3] vsock: Fix transport_* TOCTOU

[Stefano Garzarella]

On Wed, Jul 02, 2025 at 03:38:44PM +0200, Michal Luczaj wrote:
>Transport assignment may race with module unload. Protect new_transport
>from becoming a stale pointer.
>
>This also takes care of an insecure call in vsock_use_local_transport();
>add a lockdep assert.
>
>BUG: unable to handle page fault for address: fffffbfff8056000
>Oops: Oops: 0000 [#1] SMP KASAN
>RIP: 0010:vsock_assign_transport+0x366/0x600
>Call Trace:
> vsock_connect+0x59c/0xc40
> __sys_connect+0xe8/0x100
> __x64_sys_connect+0x6e/0xc0
> do_syscall_64+0x92/0x1c0
> entry_SYSCALL_64_after_hwframe+0x4b/0x53
>
>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> net/vmw_vsock/af_vsock.c | 28 +++++++++++++++++++++++-----
> 1 file changed, 23 insertions(+), 5 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 39473b9e0829f240045262aef00cbae82a425dcc..9b2af5c63f7c2ae575c160415bd77208a3980835 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -407,6 +407,8 @@ EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
>
> static bool vsock_use_local_transport(unsigned int remote_cid)
> {
>+	lockdep_assert_held(&vsock_register_mutex);
>+
> 	if (!transport_local)
> 		return false;
>
>@@ -464,6 +466,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>
> 	remote_flags = vsk->remote_addr.svm_flags;
>
>+	mutex_lock(&vsock_register_mutex);
>+
> 	switch (sk->sk_type) {
> 	case SOCK_DGRAM:
> 		new_transport = transport_dgram;
>@@ -479,12 +483,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 			new_transport = transport_h2g;
> 		break;
> 	default:
>-		return -ESOCKTNOSUPPORT;
>+		ret = -ESOCKTNOSUPPORT;
>+		goto err;
> 	}
>
> 	if (vsk->transport) {
>-		if (vsk->transport == new_transport)
>-			return 0;
>+		if (vsk->transport == new_transport) {
>+			ret = 0;
>+			goto err;
>+		}
>
> 		/* transport->release() must be called with sock lock acquired.
> 		 * This path can only be taken during vsock_connect(), where we
>@@ -508,8 +515,16 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 	/* We increase the module refcnt to prevent the transport unloading
> 	 * while there are open sockets assigned to it.
> 	 */
>-	if (!new_transport || !try_module_get(new_transport->module))
>-		return -ENODEV;
>+	if (!new_transport || !try_module_get(new_transport->module)) {
>+		ret = -ENODEV;
>+		goto err;
>+	}
>+
>+	/* It's safe to release the mutex after a successful try_module_get().
>+	 * Whichever transport `new_transport` points at, it won't go await

Little typo, s/await/away

Up to you to resend or not. My R-b stay for both cases.

Thanks,
Stefano

>+	 * until the last module_put() below or in vsock_deassign_transport().
>+	 */
>+	mutex_unlock(&vsock_register_mutex);
>
> 	if (sk->sk_type == SOCK_SEQPACKET) {
> 		if (!new_transport->seqpacket_allow ||
>@@ -528,6 +543,9 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 	vsk->transport = new_transport;
>
> 	return 0;
>+err:
>+	mutex_unlock(&vsock_register_mutex);
>+	return ret;
> }
> EXPORT_SYMBOL_GPL(vsock_assign_transport);
>
>
>-- 
>2.49.0
>

Re: [PATCH net v3 3/3] vsock: Fix IOCTL_VM_SOCKETS_GET_LOCAL_CID to check also `transport_local`

[Stefano Garzarella]

On Wed, Jul 02, 2025 at 03:38:45PM +0200, Michal Luczaj wrote:
>Support returning VMADDR_CID_LOCAL in case no other vsock transport is
>available.
>
>Fixes: 0e12190578d0 ("vsock: add local transport support in the vsock core")
>Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
>Signed-off-by: Michal Luczaj <mhal@rbox.co>
>---
> net/vmw_vsock/af_vsock.c | 2 ++
> 1 file changed, 2 insertions(+)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 9b2af5c63f7c2ae575c160415bd77208a3980835..c8398f9cec5296e07395df8e7ad0f52b8ceb65d5 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -2581,6 +2581,8 @@ static long vsock_dev_do_ioctl(struct file *filp,
> 		cid = vsock_registered_transport_cid(&transport_g2h);
> 		if (cid == VMADDR_CID_ANY)
> 			cid = vsock_registered_transport_cid(&transport_h2g);
>+		if (cid == VMADDR_CID_ANY)
>+			cid = vsock_registered_transport_cid(&transport_local);
>
> 		if (put_user(cid, p) != 0)
> 			retval = -EFAULT;
>
>-- 
>2.49.0
>

Re: [PATCH net v3 2/3] vsock: Fix transport_* TOCTOU

[Michal Luczaj]

On 7/3/25 10:20, Stefano Garzarella wrote:
> On Wed, Jul 02, 2025 at 03:38:44PM +0200, Michal Luczaj wrote:
>> Transport assignment may race with module unload. Protect new_transport
>>from becoming a stale pointer.
>>
>> This also takes care of an insecure call in vsock_use_local_transport();
>> add a lockdep assert.
>>
>> BUG: unable to handle page fault for address: fffffbfff8056000
>> Oops: Oops: 0000 [#1] SMP KASAN
>> RIP: 0010:vsock_assign_transport+0x366/0x600
>> Call Trace:
>> vsock_connect+0x59c/0xc40
>> __sys_connect+0xe8/0x100
>> __x64_sys_connect+0x6e/0xc0
>> do_syscall_64+0x92/0x1c0
>> entry_SYSCALL_64_after_hwframe+0x4b/0x53
>>
>> Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>> Signed-off-by: Michal Luczaj <mhal@rbox.co>
>> ---
>> net/vmw_vsock/af_vsock.c | 28 +++++++++++++++++++++++-----
>> 1 file changed, 23 insertions(+), 5 deletions(-)
>>
>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>> index 39473b9e0829f240045262aef00cbae82a425dcc..9b2af5c63f7c2ae575c160415bd77208a3980835 100644
>> --- a/net/vmw_vsock/af_vsock.c
>> +++ b/net/vmw_vsock/af_vsock.c
>> @@ -407,6 +407,8 @@ EXPORT_SYMBOL_GPL(vsock_enqueue_accept);
>>
>> static bool vsock_use_local_transport(unsigned int remote_cid)
>> {
>> +	lockdep_assert_held(&vsock_register_mutex);
>> +
>> 	if (!transport_local)
>> 		return false;
>>
>> @@ -464,6 +466,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>>
>> 	remote_flags = vsk->remote_addr.svm_flags;
>>
>> +	mutex_lock(&vsock_register_mutex);
>> +
>> 	switch (sk->sk_type) {
>> 	case SOCK_DGRAM:
>> 		new_transport = transport_dgram;
>> @@ -479,12 +483,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>> 			new_transport = transport_h2g;
>> 		break;
>> 	default:
>> -		return -ESOCKTNOSUPPORT;
>> +		ret = -ESOCKTNOSUPPORT;
>> +		goto err;
>> 	}
>>
>> 	if (vsk->transport) {
>> -		if (vsk->transport == new_transport)
>> -			return 0;
>> +		if (vsk->transport == new_transport) {
>> +			ret = 0;
>> +			goto err;
>> +		}
>>
>> 		/* transport->release() must be called with sock lock acquired.
>> 		 * This path can only be taken during vsock_connect(), where we
>> @@ -508,8 +515,16 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>> 	/* We increase the module refcnt to prevent the transport unloading
>> 	 * while there are open sockets assigned to it.
>> 	 */
>> -	if (!new_transport || !try_module_get(new_transport->module))
>> -		return -ENODEV;
>> +	if (!new_transport || !try_module_get(new_transport->module)) {
>> +		ret = -ENODEV;
>> +		goto err;
>> +	}
>> +
>> +	/* It's safe to release the mutex after a successful try_module_get().
>> +	 * Whichever transport `new_transport` points at, it won't go await
> 
> Little typo, s/await/away
> 
> Up to you to resend or not. My R-b stay for both cases.

Arrgh, thanks. I'll fix it.

pw-bot: changes-requested