linux-kernel - Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

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Message-ID: <2024061609-breezy-magnitude-8edf@gregkh>
Date: Sun, 16 Jun 2024 12:02:48 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Zijun Hu <quic_zijuhu@...cinc.com>
Cc: rafael@...nel.org, andriy.shevchenko@...ux.intel.com, brgl@...ev.pl,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with
 wrong size

On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
> @total_new_size, and it will cause more memory to be allocated
> than required, fixed by using @new_size as alloc_dr()'s argument.
> 
> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
> ---
>  drivers/base/devres.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index 3df0025d12aa..1cf87ddf1f55 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
>  	 */
>  	new_dr = alloc_dr(devm_kmalloc_release,
> -			  total_new_size, gfp, dev_to_node(dev));
> +			  new_size, gfp, dev_to_node(dev));

Wait, are you sure?  Did you properly test this?  What is the actual
savings and how do you handle the fact that you are now not allocating
the space reserved for the devres structure itself?

thanks,

greg k-h