[PATCH v2 0/2] scsi: leapraid: fix firmware log mmap lifetime

[PATCH v2 0/2] scsi: leapraid: fix firmware log mmap lifetime

[Linmao Li]

The firmware log mmap path has two related lifetime issues.  VMA clones
drop Scsi_Host references that they never acquired, and device removal
can free the coherent log buffer while mmap is still setting up a VMA.

Patch 1 gives each VMA its own host device reference.  Patch 2 claims a
temporary mmap activity reference under the adapter-list lock so teardown
cannot miss an in-progress mapping.

Patch 2 depends on patch 1: patch 1 keeps adapter non-NULL on the
successful mmap path, allowing patch 2 to drop the temporary mmap
reference at out_put.  Applied alone, patch 2 would leak that reference
and make teardown wait indefinitely.

Neither patch has been tested on hardware; both are derived from the
reference counting and locking in the code.

Changes in v2:
- 2/2: keep the return type and function name of
  leapraid_ctl_lookup_adapter() on one line, the declaration fits in
  the line-length limit (Dongdong Hao)
- 1/2: unchanged

v1: https://lore.kernel.org/all/20260811112001.1158587-1-lilinmao@kylinos.cn/

Linmao Li (2):
  scsi: leapraid: balance host references for firmware log VMAs
  scsi: leapraid: serialize firmware log mmap with teardown

 drivers/scsi/leapraid/leapraid_app.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)


base-commit: 376a3960e5efe85ff765abfb5b5b7e4655ad6aed
-- 
2.25.1

[PATCH v2 1/2] scsi: leapraid: balance host references for firmware log VMAs

[Linmao Li]

leapraid_fw_mmap() keeps the Scsi_Host reference obtained while
looking up the adapter for the lifetime of the initial VMA.  The VMA
close callback drops that reference.

The open callback is also invoked when a VMA is duplicated or split,
but it only increments mmap_refcnt.  Since every corresponding close
callback drops a host reference, cloning the mapping can release the
host while another VMA still refers to the adapter.

Take a host device reference for every VMA open and release the lookup
reference once the initial mapping has acquired its own reference.  Use
get_device() because a VMA can be cloned after the host enters SHOST_DEL;
an existing VMA still pins the host at that point and open cannot fail.

Fixes: 5597088c9e79 ("scsi: leapraid: Add new SCSI driver")
Signed-off-by: Linmao Li <lilinmao@kylinos.cn>
---
 drivers/scsi/leapraid/leapraid_app.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/leapraid/leapraid_app.c b/drivers/scsi/leapraid/leapraid_app.c
index 742f19c07fcbb..841027ce2501c 100644
--- a/drivers/scsi/leapraid/leapraid_app.c
+++ b/drivers/scsi/leapraid/leapraid_app.c
@@ -697,6 +697,7 @@ static void leapraid_fw_mmap_open(struct vm_area_struct *vma)
 	if (!adapter)
 		return;
 
+	get_device(&adapter->shost->shost_gendev);
 	atomic_inc(&adapter->fw_log_desc.mmap_refcnt);
 }
 
@@ -767,7 +768,6 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
 	vma->vm_private_data = adapter;
 	vma->vm_ops = &leapraid_fw_mmap_vm_ops;
 	leapraid_fw_mmap_open(vma);
-	adapter = NULL;
 
 	rc = 0;
 out_put:
-- 
2.25.1

[PATCH v2 2/2] scsi: leapraid: serialize firmware log mmap with teardown

[Linmao Li]

leapraid_fw_log_exit() waits for mmap_refcnt to reach zero before it
frees the firmware log buffer.  leapraid_fw_mmap() checks
host_removing, but it does not increment mmap_refcnt until after
dma_mmap_coherent() succeeds and the VMA open callback runs.

Removal can set host_removing and observe a zero mmap_refcnt between
the check and the VMA open.  It can then free the coherent buffer while
the mmap path is still establishing a userspace mapping of it.

Claim a temporary mmap reference while looking up the adapter under
leapraid_adapter_lock.  Removal deletes the adapter from the same
locked list after setting host_removing, so a mapping is either
rejected or included in the count that removal waits for.  Drop the
temporary reference on the common exit path, after a successful VMA
open has acquired the reference covering the VMA lifetime.

Fixes: 5597088c9e79 ("scsi: leapraid: Add new SCSI driver")
Signed-off-by: Linmao Li <lilinmao@kylinos.cn>
---
 drivers/scsi/leapraid/leapraid_app.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/leapraid/leapraid_app.c b/drivers/scsi/leapraid/leapraid_app.c
index 841027ce2501c..790a3191e9259 100644
--- a/drivers/scsi/leapraid/leapraid_app.c
+++ b/drivers/scsi/leapraid/leapraid_app.c
@@ -171,7 +171,7 @@ static int leapraid_ctl_validate_sge_offset(struct leapraid_adapter *adapter,
 	return 0;
 }
 
-static struct leapraid_adapter *leapraid_ctl_lookup_adapter(int adapter_id)
+static struct leapraid_adapter *leapraid_ctl_lookup_adapter(int adapter_id, bool track_mmap)
 {
 	struct leapraid_adapter *adapter;
 	struct Scsi_Host *shost;
@@ -184,6 +184,8 @@ static struct leapraid_adapter *leapraid_ctl_lookup_adapter(int adapter_id)
 			shost = adapter->shost;
 			if (!shost || !scsi_host_get(shost))
 				break;
+			if (track_mmap)
+				atomic_inc(&adapter->fw_log_desc.mmap_refcnt);
 			spin_unlock(&leapraid_adapter_lock);
 			return adapter;
 		}
@@ -589,7 +591,7 @@ static int leapraid_ctl_ioctl_main(struct file *file, unsigned int cmd,
 		return -EFAULT;
 	}
 
-	adapter = leapraid_ctl_lookup_adapter(ioctl_header.adapter_id);
+	adapter = leapraid_ctl_lookup_adapter(ioctl_header.adapter_id, false);
 	if (!adapter)
 		return -EFAULT;
 
@@ -728,7 +730,7 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
 
 	length = vma->vm_end - vma->vm_start;
 
-	adapter = leapraid_ctl_lookup_adapter(adapter_id);
+	adapter = leapraid_ctl_lookup_adapter(adapter_id, true);
 	if (!adapter) {
 		pr_err("%s: No adapter found!\n", __func__);
 		return -EINVAL;
@@ -771,6 +773,9 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
 
 	rc = 0;
 out_put:
+	if (adapter &&
+	    atomic_dec_and_test(&adapter->fw_log_desc.mmap_refcnt))
+		wake_up(&adapter->fw_log_desc.mmap_waitq);
 	leapraid_ctl_put_adapter(adapter);
 	return rc;
 }
-- 
2.25.1

Re: [PATCH v2 1/2] scsi: leapraid: balance host references for firmware log VMAs

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:

Pre-existing issues:
- [High] Unkillable sleep in device removal path if userspace keeps the memory mapped.
- [High] TOCTOU race in leapraid_fw_mmap allowing use-after-free of fw_log_buffer.
--

--- Patch [1]: [PATCH v2 1/2] scsi: leapraid: balance host references for firmware log VMAs ---
commit f0e08e76b84e5bcaddf6147e197d89f0cec2a4e9
Author: Linmao Li <lilinmao@kylinos.cn>

scsi: leapraid: balance host references for firmware log VMAs

leapraid_fw_mmap() keeps the Scsi_Host reference obtained while
looking up the adapter for the lifetime of the initial VMA.  The VMA
close callback drops that reference.

The open callback is also invoked when a VMA is duplicated or split,
but it only increments mmap_refcnt.  Since every corresponding close
callback drops a host reference, cloning the mapping can release the
host while another VMA still refers to the adapter.

Take a host device reference for every VMA open and release the lookup
reference once the initial mapping has acquired its own reference.  Use
get_device() because a VMA can be cloned after the host enters SHOST_DEL;
an existing VMA still pins the host at that point and open cannot fail.

> diff --git a/drivers/scsi/leapraid/leapraid_app.c b/drivers/scsi/leapraid/leapraid_app.c
> index 742f19c07fcbb..841027ce2501c 100644
> --- a/drivers/scsi/leapraid/leapraid_app.c
> +++ b/drivers/scsi/leapraid/leapraid_app.c
> @@ -697,6 +697,7 @@ static void leapraid_fw_mmap_open(struct vm_area_struct *vma)
>  	if (!adapter)
>  		return;
>  
> +	get_device(&adapter->shost->shost_gendev);
>  	atomic_inc(&adapter->fw_log_desc.mmap_refcnt);

[Severity: High]
This is a pre-existing issue, but does this create an unkillable sleep in the
device removal path?

If a user maps the firmware log buffer via mmap and never unmaps it, the
removal thread executing leapraid_fw_log_exit() in leapraid_func.c will block
indefinitely waiting for the reference count to drop to zero:

    wait_event(adapter->fw_log_desc.mmap_waitq,
               !atomic_read(&adapter->fw_log_desc.mmap_refcnt));

Since there is no mechanism to forcibly revoke the mapping, could this allow
userspace to block device removal indefinitely?

>  }
>  
> @@ -767,7 +768,6 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
>  	vma->vm_private_data = adapter;
>  	vma->vm_ops = &leapraid_fw_mmap_vm_ops;
>  	leapraid_fw_mmap_open(vma);

[Severity: High]
This isn't a bug introduced by this patch, but is there a race condition here
that allows a use-after-free of the firmware log buffer?

The buffer is mapped to user space via dma_mmap_coherent() earlier in this
function before mmap_refcnt is incremented here in leapraid_fw_mmap_open().

If a concurrent device removal preempts this thread right before
leapraid_fw_mmap_open() is called, leapraid_fw_log_exit() will see
mmap_refcnt == 0 and free the buffer via dma_free_coherent().

When the mmap thread resumes, will it have successfully mapped freed kernel
DMA memory into user space?

> -	adapter = NULL;
>  
>  	rc = 0;
>  out_put:

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260813072614.1387555-1-lilinmao@kylinos.cn?part=1

Re: [PATCH v2 2/2] scsi: leapraid: serialize firmware log mmap with teardown

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Device removal and module unloading can be permanently blocked by a userspace process holding an open memory mapping.
--

--- Patch [2]: [PATCH v2 2/2] scsi: leapraid: serialize firmware log mmap with teardown ---
commit 3180bb0e1579b0aca65c2e7927f3bdc91744a626
Author: Linmao Li <lilinmao@kylinos.cn>

scsi: leapraid: serialize firmware log mmap with teardown

This patch addresses a race condition where a firmware log buffer could be
freed during device removal while a concurrent mmap operation is
establishing a userspace mapping. It claims a temporary mmap reference
while looking up the adapter, and drops it on the exit path.

> diff --git a/drivers/scsi/leapraid/leapraid_app.c b/drivers/scsi/leapraid/leapraid_app.c
> index 841027ce2501c..790a3191e9259 100644
> --- a/drivers/scsi/leapraid/leapraid_app.c
> +++ b/drivers/scsi/leapraid/leapraid_app.c
[ ... ]
> @@ -771,6 +773,9 @@ static int leapraid_fw_mmap(struct file *filp, struct vm_area_struct *vma)
>  
>  	rc = 0;
>  out_put:
> +	if (adapter &&
> +	    atomic_dec_and_test(&adapter->fw_log_desc.mmap_refcnt))
> +		wake_up(&adapter->fw_log_desc.mmap_waitq);

[Severity: High]
This is a pre-existing issue, but can this userspace-controlled reference
count block device removal and module unloading permanently?

Since a userspace process can hold the VMA open indefinitely, and device
removal waits unconditionally in leapraid_fw_log_exit() for the count to
reach zero:

drivers/scsi/leapraid/leapraid_func.c:leapraid_fw_log_exit() {
    ...
    wait_event(adapter->fw_log_desc.mmap_waitq,
               !atomic_read(&adapter->fw_log_desc.mmap_refcnt));
    ...
}

Could a buggy or malicious userspace process that never unmaps the memory
cause the kernel thread handling PCI hotplug or sysfs unbind to hang
forever without a timeout?

>  	leapraid_ctl_put_adapter(adapter);
>  	return rc;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260813072614.1387555-1-lilinmao@kylinos.cn?part=2