linux-kernel - Re: [PATCH] PCI: Always initialize dev in pciconfig

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Date:   Tue, 3 Aug 2021 16:56:21 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] PCI: Always initialize dev in pciconfig_read

On Tue, Aug 03, 2021 at 01:08:36PM -0700, Nathan Chancellor wrote:
> Clang warns:
> 
> drivers/pci/syscall.c:25:6: warning: variable 'dev' is used
> uninitialized whenever 'if' condition is true
> [-Wsometimes-uninitialized]
>         if (!capable(CAP_SYS_ADMIN))
>             ^~~~~~~~~~~~~~~~~~~~~~~
> drivers/pci/syscall.c:81:14: note: uninitialized use occurs here
>         pci_dev_put(dev);
>                     ^~~
> drivers/pci/syscall.c:25:2: note: remove the 'if' if its condition is
> always false
>         if (!capable(CAP_SYS_ADMIN))
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/pci/syscall.c:18:21: note: initialize the variable 'dev' to
> silence this warning
>         struct pci_dev *dev;
>                            ^
>                             = NULL
> 1 warning generated.
> 
> pci_dev_put accounts for a NULL pointer so initialize dev to NULL before
> the capability check so that there is no use of uninitialized memory.
> 
> Fixes: 61a6199787d9 ("PCI: Return ~0 data on pciconfig_read() CAP_SYS_ADMIN failure")
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Squashed in locally, thanks!

> ---
>  drivers/pci/syscall.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
> index 525f16caed1d..61a6fe3cde21 100644
> --- a/drivers/pci/syscall.c
> +++ b/drivers/pci/syscall.c
> @@ -22,6 +22,7 @@ SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn,
>  	int err, cfg_ret;
>  
>  	err = -EPERM;
> +	dev = NULL;
>  	if (!capable(CAP_SYS_ADMIN))
>  		goto error;
>  
> 
> base-commit: 21d8e94253eb09f7c94c4db00dc714efc75b8701
> -- 
> 2.33.0.rc0
>