2023-09-10 13:15:18

by Rik van Riel

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

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: [email protected]
Signed-off-by: Rik van Riel <[email protected]>
Suggested-by: Mike Rappoport <[email protected]>
---
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

2023-09-17 07:42:43

by Mike Rapoport

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

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: [email protected]
> Signed-off-by: Rik van Riel <[email protected]>
> Suggested-by: Mike Rappoport <[email protected]>

Acked-by: Mike Rapoport (IBM) <[email protected]>

> ---
> 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.