On Thu, Jul 20, 2023 at 10:14:31AM -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")
Fixes: b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on kexec")
Acked-by: Rob Herring <robh@xxxxxxxxxx>
(I'm assuming someone else is taking this)
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
> Suggested-by: Mike Rappoport <rppt@xxxxxxxxxx>
> ---
> arch/x86/kernel/setup.c | 8 ++------
> drivers/of/kexec.c | 3 ++-
> 2 files changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index fd975a4a5200..aa0df37c1fe7 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -359,15 +359,11 @@ 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;
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index f26d2ba8a371..68278340cecf 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -184,7 +184,8 @@ int __init ima_free_kexec_buffer(void)
> if (ret)
> return ret;
>
> - return memblock_phys_free(addr, size);
> + memblock_free_late(addr, size);
> + return 0;
> }
> #endif
>
> --
> 2.41.0
>
