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Re: [Qemu-devel] [PATCH v3 2/2] loader: Fix 64-bit misaligned member acc
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/2] loader: Fix 64-bit misaligned member access |
Date: |
Fri, 25 May 2018 16:07:01 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 |
On 23/04/2018 18:25, Philippe Mathieu-Daudé wrote:
> The libfdt does not guarantee than fdt_getprop() returns a pointer
> aligned to the property size.
>
> Assuming the base of the fdt is aligned, a 32-bit property returns
> a 32-bit aligned pointer. This is however not guaranteed for 64-bit
> properties, where 64-bit loads might trigger unaligned access.
>
> Fix this issue by using the ldst (host) API, which does a local copy
> on the stack, thus guaranteeing a safe aligned access.
>
> This fixes the following ASan warning:
>
> $ mips64el-softmmu/qemu-system-mips64el -M boston -kernel vmlinux.gz.itb
> -nographic
> hw/core/loader-fit.c:108:17: runtime error: load of misaligned address
> 0x7f95cd7e4264 for type 'fdt64_t', which requires 8 byte alignment
> 0x7f95cd7e4264: note: pointer points here
> 00 00 00 3e ff ff ff ff 80 7d 2a c0 00 00 00 01 68 61 73 68 40 30 00 00
> 00 00 00 03 00 00 00 14
> ^
>
> Reported-by: AddressSanitizer
> Suggested-by: Peter Maydell <address@hidden>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> hw/core/loader-fit.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
> index 0c4a7207f4..628f854636 100644
> --- a/hw/core/loader-fit.c
> +++ b/hw/core/loader-fit.c
> @@ -102,10 +102,10 @@ static int fit_image_addr(const void *itb, int img,
> const char *name,
>
> switch (len) {
> case 4:
> - *addr = fdt32_to_cpu(*(fdt32_t *)prop);
> + *addr = fdt32_to_cpu(ldl_he_p(prop));
> return 0;
> case 8:
> - *addr = fdt64_to_cpu(*(fdt64_t *)prop);
> + *addr = fdt64_to_cpu(ldq_he_p(prop));
> return 0;
> default:
> error_printf("invalid %s address length %d\n", name, len);
>
Reviewed-by: Paolo Bonzini <address@hidden>
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