[PATCH 03/14] xfs: Don't reference the EFI after it is freed

[Brian Foster]

On 05/19/2013 07:51 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> Checking the EFI for whether it is being released from recovery
> after we've already released the known active reference is a mistake
> worthy of a brown paper bag. Fix the (now) obvious use after free
> that it can cause.
> 
> Reported-by: Dave Jones <davej at redhat.com>
> Signed-off-by: Dave Chinner <dchinner at redhat.com>
> ---

Looks good to me.

Reviewed-by: Brian Foster <bfoster at redhat.com>

>  fs/xfs/xfs_extfree_item.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
> index c0f3750..452920a 100644
> --- a/fs/xfs/xfs_extfree_item.c
> +++ b/fs/xfs/xfs_extfree_item.c
> @@ -305,11 +305,12 @@ xfs_efi_release(xfs_efi_log_item_t	*efip,
>  {
>  	ASSERT(atomic_read(&efip->efi_next_extent) >= nextents);
>  	if (atomic_sub_and_test(nextents, &efip->efi_next_extent)) {
> -		__xfs_efi_release(efip);
> -
>  		/* recovery needs us to drop the EFI reference, too */
>  		if (test_bit(XFS_EFI_RECOVERED, &efip->efi_flags))
>  			__xfs_efi_release(efip);
> +
> +		__xfs_efi_release(efip);
> +		/* efip may now have been freed, do not reference it again. */
>  	}
>  }
>  
>