Re: [PATCH 3/7] contrib/elf2dmp: Ensure segment fits in file

[Peter Maydell]

On Sun, 3 Mar 2024 at 10:53, Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
>
> This makes elf2dmp more robust against corrupted inputs.
>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
>  contrib/elf2dmp/addrspace.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/contrib/elf2dmp/addrspace.c b/contrib/elf2dmp/addrspace.c
> index 980a7aa5f8fb..d546a400dfda 100644
> --- a/contrib/elf2dmp/addrspace.c
> +++ b/contrib/elf2dmp/addrspace.c
> @@ -88,11 +88,12 @@ int pa_space_create(struct pa_space *ps, QEMU_Elf 
> *qemu_elf)
>      ps->block = g_new(struct pa_block, ps->block_nr);
>
>      for (i = 0; i < phdr_nr; i++) {
> -        if (phdr[i].p_type == PT_LOAD) {
> +        if (phdr[i].p_type == PT_LOAD && phdr[i].p_offset < qemu_elf->size) {
>              ps->block[block_i] = (struct pa_block) {
>                  .addr = (uint8_t *)qemu_elf->map + phdr[i].p_offset,
>                  .paddr = phdr[i].p_paddr,
> -                .size = phdr[i].p_filesz,
> +                .size = MIN(phdr[i].p_filesz,
> +                            qemu_elf->size - phdr[i].p_offset),

Shouldn't "p_filesz is smaller than the actual amount of data in the
file" be a failure condition? In include/hw/elf_ops.h we treat it
that way:

            mem_size = ph->p_memsz; /* Size of the ROM */
            file_size = ph->p_filesz; /* Size of the allocated data */
            data_offset = ph->p_offset; /* Offset where the data is located */

            if (file_size > 0) {
                if (g_mapped_file_get_length(mapped_file) <
                    file_size + data_offset) {
                    goto fail;
                }
                [etc]

Like that code, we could then only check if p_offset + p_filesz is off
the end of the file, rather than checking p_offset separately.

>              };
>              pa_block_align(&ps->block[block_i]);
>              block_i = ps->block[block_i].size ? (block_i + 1) : block_i;

thanks
-- PMM