Re: [PATCH] vfio/pds: replace bitmap_free with vfree

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 12 Sep 2025 15:04:18 +0000
Zilin Guan <zilin@seu.edu.cn> wrote:

> host_ack_bmp is allocated with vzalloc but is currently freed via
> bitmap_free (which ends up using kfree).  This is incorrect as
> allocation and deallocation functions should be paired.

This patch is fixing the freeing of host_seq_bmp, not host_ack_bmp.
Both are allocated with vzalloc().  The same logic applies but the
commit log is incorrect.
 
> Using mismatched alloc/free may lead to undefined behavior, memory leaks,
> or system instability.
> 
> This patch fixes the mismatch by freeing host_ack_bmp with vfree to
> match the vzalloc allocation.
> 

Fixes: f232836a9152 ("vfio/pds: Add support for dirty page tracking")

Thanks,
Alex

> Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
> ---
>  drivers/vfio/pci/pds/dirty.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/pci/pds/dirty.c b/drivers/vfio/pci/pds/dirty.c
> index c51f5e4c3dd6..481992142f79 100644
> --- a/drivers/vfio/pci/pds/dirty.c
> +++ b/drivers/vfio/pci/pds/dirty.c
> @@ -82,7 +82,7 @@ static int pds_vfio_dirty_alloc_bitmaps(struct pds_vfio_region *region,
>  
>  	host_ack_bmp = vzalloc(bytes);
>  	if (!host_ack_bmp) {
> -		bitmap_free(host_seq_bmp);
> +		vfree(host_seq_bmp);
>  		return -ENOMEM;
>  	}
>