Re: [PATCH v3 07/17] crash_dump: Fix potential double-free of keys_header

[Sourabh Jain <sourabhjain@linux.ibm.com>]

Hello Jinjie,

Coiby is handling this issue in the below patch series:
https://lore.kernel.org/all/20260828084900.1496839-2-coiby.xu@gmail.com/

Since the above patch series is all about crash_load_dm_crypt_keys, 
could you
please consider dropping this patch from your series and reviewing his patch
instead?

Thanks,
Sourabh Jain

On 26/08/26 14:55, Jinjie Ruan wrote:
> `keys_header` was freed in `build_keys_header()` without being reset
> to NULL, and the error path in `crash_load_dm_crypt_keys()` freed it
> unconditionally even when reused, leading to double-free or
> use-after-free.
>
> Add `free_keys_header()` to centralize freeing and NULL-setting.
> Use it in `build_keys_header()` and only free in the error path when
> the header was newly built (`!is_dm_key_reused`).
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Baoquan He <bhe@redhat.com>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
> Cc: Pratyush Yadav <pratyush@kernel.org>
> Cc: Dave Young <ruirui.yang@linux.dev>
> Cc: stable@vger.kernel.org
> Fixes: e3a84be1ec2f ("arm64,ppc64le/kdump: pass dm-crypt keys to kdump kernel")
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>   kernel/crash_dump_dm_crypt.c | 15 +++++++++++----
>   1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
> index c685497cd470..ed0960ff0987 100644
> --- a/kernel/crash_dump_dm_crypt.c
> +++ b/kernel/crash_dump_dm_crypt.c
> @@ -363,15 +363,21 @@ static struct configfs_subsystem config_keys_subsys = {
>   	},
>   };
>   
> +static void free_keys_header(void)
> +{
> +	if (keys_header) {
> +		kvfree(keys_header);
> +		keys_header = NULL;
> +	}
> +}
> +
>   static int build_keys_header(void)
>   {
>   	struct config_item *item = NULL;
>   	struct config_key *key;
>   	int i, r;
>   
> -	if (keys_header != NULL)
> -		kvfree(keys_header);
> -
> +	free_keys_header();
>   	keys_header = kzalloc(get_keys_header_size(key_count), GFP_KERNEL);
>   	if (!keys_header)
>   		return -ENOMEM;
> @@ -441,7 +447,8 @@ int crash_load_dm_crypt_keys(struct kimage *image)
>   	r = kexec_add_buffer(&kbuf);
>   	if (r) {
>   		pr_err("Failed to call kexec_add_buffer, ret=%d\n", r);
> -		kvfree((void *)kbuf.buffer);
> +		if (!is_dm_key_reused)
> +			free_keys_header();
>   		return r;
>   	}
>   	image->dm_crypt_keys_addr = kbuf.mem;