[PATCH v2] efi_loader: fix use after free in efi_exit() with tcg2

[kojima.masahisa at socionext.com]

Hi Vincent,

> -----Original Message-----
> From: Vincent Stehlé <vincent.stehle at arm.com>
> Sent: Wednesday, January 28, 2026 1:19 AM
> Subject: [PATCH v2] efi_loader: fix use after free in efi_exit() with tcg2
> 
> The efi_exit() function frees the loaded image memory by calling
> efi_delete_image(). However, when CONFIG_EFI_TCG2_PROTOCOL is
> enabled, the
> image_obj->image_type structure member is accessed after the memory has
> been freed.
> 
> Fix this by performing the tcg2 measurement before the image deletion.
> 
> Fixes: 8fc4e0b4273a ("efi_loader: add boot variable measurement")
> Suggested-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> Signed-off-by: Vincent Stehlé <vincent.stehle at arm.com>
> Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: Masahisa Kojima <kojima.masahisa at socionext.com>
> ---
> 
> Hi,
> 
> Here is a respin after feedbacks. [1]
> 
> Changes for v2:
> - Move the event measurement before image deletion instead of keeping a
>   copy of image_type (thanks Ilias!)
> 
> This can be verified with sandbox_defconfig + CONFIG_VALGRIND=y and the
> following command:
> 
>   valgrind --suppressions=scripts/u-boot.supp \
>     ./u-boot -T -c "setenv efi_selftest start image return; \
>                     bootefi selftest"
> 
> This was lightly tested for regression with sandbox_defconfig and the
> following commands:
> 
>   ./u-boot -T -c "ut measurement"
> 
>   ./test/py/test.py --build-dir="$PWD" -s -k "test_efi_bootmgr \
> 	or test_efi_loader or test_efi_selftest or test_efi_secboot"
> 
> Adding some instrumentation in efi_exit() and tcg2_log_append() shows no
> change in the event measurements sequence.
> 
> [1]
> https://lore.kernel.org/u-boot/20260123105814.1083834-1-vincent.stehle@ar
> m.com/
> 
>  lib/efi_loader/efi_boottime.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index ddc935d2240..b424d924896 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -3494,12 +3494,6 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t
> image_handle,
>  		if (ret != EFI_SUCCESS)
>  			EFI_PRINT("%s: out of memory\n", __func__);
>  	}
> -	/* efi_delete_image() frees image_obj. Copy before the call. */
> -	exit_jmp = image_obj->exit_jmp;
> -	*image_obj->exit_status = exit_status;
> -	if (image_obj->image_type ==
> IMAGE_SUBSYSTEM_EFI_APPLICATION ||
> -	    exit_status != EFI_SUCCESS)
> -		efi_delete_image(image_obj, loaded_image_protocol);
> 
>  	if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL)) {
>  		if (image_obj->image_type ==
> IMAGE_SUBSYSTEM_EFI_APPLICATION) {
> @@ -3510,6 +3504,13 @@ static efi_status_t EFIAPI efi_exit(efi_handle_t
> image_handle,
>  		}
>  	}
> 
> +	/* efi_delete_image() frees image_obj. Copy before the call. */
> +	exit_jmp = image_obj->exit_jmp;
> +	*image_obj->exit_status = exit_status;
> +	if (image_obj->image_type ==
> IMAGE_SUBSYSTEM_EFI_APPLICATION ||
> +	    exit_status != EFI_SUCCESS)
> +		efi_delete_image(image_obj, loaded_image_protocol);
> +
>  	/* Make sure entry/exit counts for EFI world cross-overs match */
>  	EFI_EXIT(exit_status);

Thanks for the fix.
Acked-by: Masahisa Kojima <kojima.masahisa at socionext.com>

Best Regards,
Masahisa Kojima

> 
> --
> 2.51.0