On Thu, Aug 17, 2023 at 01:57:59PM -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")
Didn't powerpc have the same issue before this commit? The move changed
memblock_free() to memblock_phys_free(), but otherwise the code was the
same. But wait, the old code looks broken as it reads a phys addr from
DT and passes that to memblock_free() which wants a virt addr. Probably
should have fixed that before moving things. I guess the Fixes here is
right and powerpc needs a different backport for before commit
fee3ff99bc67 if they care.
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
> Suggested-by: Mike Rappoport <rppt@xxxxxxxxxx>
> ---
> drivers/of/kexec.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> 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
>
