Re: [PATCH] x86,kexec,ima: use memblock_free_late from ima_free_kexec_buffer

[Mike Rapoport <rppt@kernel.org>]

On Fri, Sep 08, 2023 at 11:31:27PM -0400, Rik van Riel wrote:
> The code calling ima_free_kexec_buffer runs long after the memblock
> allocator has already been torn down, potentially resulting in a use
> after free in memblock_isolate_range.
> 
> With KASAN or KFENCE, this use after free will result in a BUG
> from the idle task, and a subsequent kernel panic.
> 
> Switch ima_free_kexec_buffer over to memblock_free_late to avoid
> that issue.
> 
> Fixes: fee3ff99bc67 ("powerpc: Move arch independent ima kexec functions to drivers/of/kexec.c")
> Cc: stable@kernel.org
> Signed-off-by: Rik van Riel <riel@surriel.com>
> Suggested-by: Mike Rappoport <rppt@kernel.org>

Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  arch/x86/kernel/setup.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index b9145a63da77..b098b1fa2470 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -358,15 +358,11 @@ static void __init add_early_ima_buffer(u64 phys_addr)
>  #if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE)
>  int __init ima_free_kexec_buffer(void)
>  {
> -	int rc;
> -
>  	if (!ima_kexec_buffer_size)
>  		return -ENOENT;
>  
> -	rc = memblock_phys_free(ima_kexec_buffer_phys,
> -				ima_kexec_buffer_size);
> -	if (rc)
> -		return rc;
> +	memblock_free_late(ima_kexec_buffer_phys,
> +			   ima_kexec_buffer_size);
>  
>  	ima_kexec_buffer_phys = 0;
>  	ima_kexec_buffer_size = 0;
> -- 
> 2.41.0
> 
> 

-- 
Sincerely yours,
Mike.