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Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access |
Date: |
Sun, 22 Apr 2018 11:41:20 +0100 |
On 21 April 2018 at 22:16, Philippe Mathieu-Daudé <address@hidden> wrote:
> 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
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> hw/core/loader-fit.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
> index 0c4a7207f4..1a69697f89 100644
> --- a/hw/core/loader-fit.c
> +++ b/hw/core/loader-fit.c
> @@ -93,6 +93,8 @@ static int fit_image_addr(const void *itb, int img, const
> char *name,
> hwaddr *addr)
> {
> const void *prop;
> + fdt32_t v32;
> + fdt64_t v64;
> int len;
>
> prop = fdt_getprop(itb, img, name, &len);
> @@ -102,10 +104,12 @@ static int fit_image_addr(const void *itb, int img,
> const char *name,
>
> switch (len) {
> case 4:
> - *addr = fdt32_to_cpu(*(fdt32_t *)prop);
> + memcpy(&v32, prop, sizeof(v32));
> + *addr = fdt32_to_cpu(v32);
If we need to do an unaligned load, then ldl_p() is the
right way to do it. (We could also just do
*addr = ldl_be_p(prop) but we maybe don't want to
bake in knowledge that FDT is big-endian).
This does make me suspicious that maybe we're not using
the fdt APIs right here though. Since 'prop' is the return
value of fdt_getprop(), shouldn't libfdt be providing
APIs for "give me the fdt32 here" that don't require
the libfdt user to either implement its own unaligned
access helpers or invoke C undefined behaviour? David,
any suggestions?
(Similarly with the fdt64 access and ldq_p.)
thanks
-- PMM
- [Qemu-devel] [PATCH] loader: Fix misaligned member access, Philippe Mathieu-Daudé, 2018/04/21
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access,
Peter Maydell <=
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, David Gibson, 2018/04/22
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Philippe Mathieu-Daudé, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Peter Maydell, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Philippe Mathieu-Daudé, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Philippe Mathieu-Daudé, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Peter Maydell, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Philippe Mathieu-Daudé, 2018/04/23
- Re: [Qemu-devel] [PATCH] loader: Fix misaligned member access, Peter Maydell, 2018/04/23