linux-kernel - Re: [PATCH] mtd: ck804xrom: fix missing pci device put in error paths

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Message-ID: <20200827144600.2ec7c4ab@xps13>
Date:   Thu, 27 Aug 2020 14:46:00 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     James Bond <jameslouisebond@...il.com>
Cc:     Vignesh Raghavendra <vigneshr@...com>,
        Arnd Bergmann <arnd@...db.de>,
        Ryan Jackson <rjackson@...i.com>,
        Richard Weinberger <richard@....at>,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH] mtd: ck804xrom: fix missing pci device put in error
 paths

Hi James,

James Bond <jameslouisebond@...il.com> wrote on Fri, 21 Aug 2020
02:05:36 -0500:

> pci_dev_get increases the refcount of "pdev".
> In the error paths, pci_dev_put should be called
> to handle the "pdev" and decrease the corresponding refcount.
> 
> Fixes: 90afffc8bd79 ("[MTD] [MAPS] Support for BIOS flash chips on the nvidia ck804 southbridge")
> Signed-off-by: James Bond <jameslouisebond@...il.com>
> ---
>  drivers/mtd/maps/ck804xrom.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/mtd/maps/ck804xrom.c b/drivers/mtd/maps/ck804xrom.c
> index 460494212f6a..16af8b5ee653 100644
> --- a/drivers/mtd/maps/ck804xrom.c
> +++ b/drivers/mtd/maps/ck804xrom.c
> @@ -195,6 +195,7 @@ static int __init ck804xrom_init_one(struct pci_dev *pdev,
>  	if (!window->virt) {
>  		printk(KERN_ERR MOD_NAME ": ioremap(%08lx, %08lx) failed\n",
>  			window->phys, window->size);
> +		pci_dev_put(pdev);
>  		goto out;
>  	}
>  
> @@ -222,6 +223,7 @@ static int __init ck804xrom_init_one(struct pci_dev *pdev,
>  
>  		if (!map) {
>  			printk(KERN_ERR MOD_NAME ": kmalloc failed");
> +			pci_dev_put(pdev);
>  			goto out;
>  		}
>  		memset(map, 0, sizeof(*map));
> @@ -295,6 +297,7 @@ static int __init ck804xrom_init_one(struct pci_dev *pdev,
>  		if (mtd_device_register(map->mtd, NULL, 0)) {
>  			map_destroy(map->mtd);
>  			map->mtd = NULL;
> +			pci_dev_put(pdev);
>  			goto out;
>  		}
>  

I suppose in these three cases, the window->maps list will be empty and
you will end up returning -ENODEV and the bottom of the function? If
yes, it woudl probably be better to move these pci_dev_put() calls to
this location.

Otherwise, it might bit interesting to clean up a little bit the error
path and perhaps have a distinct success vs. failure path.


Thanks,
Miquèl