[PATCH] ntb: idt: Fix error handling in idt_pci_driver_init()

[PATCH] ntb: idt: Fix error handling in idt_pci_driver_init()

[Yuan Can]

A problem about ntb_hw_idt create debugfs failed is triggered with the
following log given:

 [ 1236.637636] IDT PCI-E Non-Transparent Bridge Driver 2.0
 [ 1236.639292] debugfs: Directory 'ntb_hw_idt' with parent '/' already present!

The reason is that idt_pci_driver_init() returns pci_register_driver()
directly without checking its return value, if pci_register_driver()
failed, it returns without destroy the newly created debugfs, resulting
the debugfs of ntb_hw_idt can never be created later.

 idt_pci_driver_init()
   debugfs_create_dir() # create debugfs directory
   pci_register_driver()
     driver_register()
       bus_add_driver()
         priv = kzalloc(...) # OOM happened
   # return without destroy debugfs directory

Fix by removing debugfs when pci_register_driver() returns error.

Fixes: bf2a952d31d2 ("NTB: Add IDT 89HPESxNTx PCIe-switches support")
Signed-off-by: Yuan Can <yuancan@huawei.com>
---
 drivers/ntb/hw/idt/ntb_hw_idt.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/ntb/hw/idt/ntb_hw_idt.c b/drivers/ntb/hw/idt/ntb_hw_idt.c
index 0ed6f809ff2e..51799fccf840 100644
--- a/drivers/ntb/hw/idt/ntb_hw_idt.c
+++ b/drivers/ntb/hw/idt/ntb_hw_idt.c
@@ -2891,6 +2891,7 @@ static struct pci_driver idt_pci_driver = {
 
 static int __init idt_pci_driver_init(void)
 {
+	int ret;
 	pr_info("%s %s\n", NTB_DESC, NTB_VER);
 
 	/* Create the top DebugFS directory if the FS is initialized */
@@ -2898,7 +2899,11 @@ static int __init idt_pci_driver_init(void)
 		dbgfs_topdir = debugfs_create_dir(KBUILD_MODNAME, NULL);
 
 	/* Register the NTB hardware driver to handle the PCI device */
-	return pci_register_driver(&idt_pci_driver);
+	ret = pci_register_driver(&idt_pci_driver);
+	if (ret)
+		debugfs_remove_recursive(dbgfs_topdir);
+
+	return ret;
 }
 module_init(idt_pci_driver_init);
 
-- 
2.17.1

Re: [PATCH] ntb: idt: Fix error handling in idt_pci_driver_init()

[Serge Semin]

On Sat, Nov 05, 2022 at 09:43:01AM +0000, Yuan Can wrote:
> A problem about ntb_hw_idt create debugfs failed is triggered with the
> following log given:
> 
>  [ 1236.637636] IDT PCI-E Non-Transparent Bridge Driver 2.0
>  [ 1236.639292] debugfs: Directory 'ntb_hw_idt' with parent '/' already present!
> 
> The reason is that idt_pci_driver_init() returns pci_register_driver()
> directly without checking its return value, if pci_register_driver()
> failed, it returns without destroy the newly created debugfs, resulting
> the debugfs of ntb_hw_idt can never be created later.
> 
>  idt_pci_driver_init()
>    debugfs_create_dir() # create debugfs directory
>    pci_register_driver()
>      driver_register()
>        bus_add_driver()
>          priv = kzalloc(...) # OOM happened
>    # return without destroy debugfs directory
> 
> Fix by removing debugfs when pci_register_driver() returns error.

Indeed. Thanks for the patch.
Acked-by: Serge Semin <fancer.lancer@gmail.com>

-Serge(y)

> 
> Fixes: bf2a952d31d2 ("NTB: Add IDT 89HPESxNTx PCIe-switches support")
> Signed-off-by: Yuan Can <yuancan@huawei.com>
> ---
>  drivers/ntb/hw/idt/ntb_hw_idt.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ntb/hw/idt/ntb_hw_idt.c b/drivers/ntb/hw/idt/ntb_hw_idt.c
> index 0ed6f809ff2e..51799fccf840 100644
> --- a/drivers/ntb/hw/idt/ntb_hw_idt.c
> +++ b/drivers/ntb/hw/idt/ntb_hw_idt.c
> @@ -2891,6 +2891,7 @@ static struct pci_driver idt_pci_driver = {
>  
>  static int __init idt_pci_driver_init(void)
>  {
> +	int ret;
>  	pr_info("%s %s\n", NTB_DESC, NTB_VER);
>  
>  	/* Create the top DebugFS directory if the FS is initialized */
> @@ -2898,7 +2899,11 @@ static int __init idt_pci_driver_init(void)
>  		dbgfs_topdir = debugfs_create_dir(KBUILD_MODNAME, NULL);
>  
>  	/* Register the NTB hardware driver to handle the PCI device */
> -	return pci_register_driver(&idt_pci_driver);
> +	ret = pci_register_driver(&idt_pci_driver);
> +	if (ret)
> +		debugfs_remove_recursive(dbgfs_topdir);
> +
> +	return ret;
>  }
>  module_init(idt_pci_driver_init);
>  
> -- 
> 2.17.1
>