Re: [PATCH v10 6/8] linux-user/elfload: Move PT_INTERP detection to first loop

[Philippe Mathieu-Daudé]

On 10/2/20 11:59 PM, Richard Henderson wrote:
> For BTI, we need to know if the executable is static or dynamic,
> which means looking for PT_INTERP earlier.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/elfload.c | 60 +++++++++++++++++++++++---------------------
>  1 file changed, 31 insertions(+), 29 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 735ebfa190..6b422990ff 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2421,8 +2421,10 @@ static void load_elf_image(const char *image_name, int 
> image_fd,
>  
>      mmap_lock();
>  
> -    /* Find the maximum size of the image and allocate an appropriate
> -       amount of memory to handle that.  */
> +    /*
> +     * Find the maximum size of the image and allocate an appropriate
> +     * amount of memory to handle that.  Locate the interpreter, if any.
> +     */
>      loaddr = -1, hiaddr = 0;
>      info->alignment = 0;
>      for (i = 0; i < ehdr->e_phnum; ++i) {
> @@ -2438,6 +2440,33 @@ static void load_elf_image(const char *image_name, int 
> image_fd,
>              }
>              ++info->nsegs;
>              info->alignment |= eppnt->p_align;
> +        } else if (eppnt->p_type == PT_INTERP && pinterp_name) {
> +            char *interp_name;
> +
> +            if (*pinterp_name) {
> +                errmsg = "Multiple PT_INTERP entries";
> +                goto exit_errmsg;
> +            }
> +            interp_name = malloc(eppnt->p_filesz);
> +            if (!interp_name) {
> +                goto exit_perror;
> +            }
> +
> +            if (eppnt->p_offset + eppnt->p_filesz <= BPRM_BUF_SIZE) {
> +                memcpy(interp_name, bprm_buf + eppnt->p_offset,
> +                       eppnt->p_filesz);
> +            } else {
> +                retval = pread(image_fd, interp_name, eppnt->p_filesz,
> +                               eppnt->p_offset);
> +                if (retval != eppnt->p_filesz) {

Preexisting, free(interp_name)?

> +                    goto exit_perror;
> +                }
> +            }
> +            if (interp_name[eppnt->p_filesz - 1] != 0) {
> +                errmsg = "Invalid PT_INTERP entry";

Ditto, otherwise:
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> +                goto exit_errmsg;
> +            }
> +            *pinterp_name = interp_name;
>          }
>      }
>  
> @@ -2590,33 +2619,6 @@ static void load_elf_image(const char *image_name, int 
> image_fd,
>              if (vaddr_em > info->brk) {
>                  info->brk = vaddr_em;
>              }
> -        } else if (eppnt->p_type == PT_INTERP && pinterp_name) {
> -            char *interp_name;
> -
> -            if (*pinterp_name) {
> -                errmsg = "Multiple PT_INTERP entries";
> -                goto exit_errmsg;
> -            }
> -            interp_name = malloc(eppnt->p_filesz);
> -            if (!interp_name) {
> -                goto exit_perror;
> -            }
> -
> -            if (eppnt->p_offset + eppnt->p_filesz <= BPRM_BUF_SIZE) {
> -                memcpy(interp_name, bprm_buf + eppnt->p_offset,
> -                       eppnt->p_filesz);
> -            } else {
> -                retval = pread(image_fd, interp_name, eppnt->p_filesz,
> -                               eppnt->p_offset);
> -                if (retval != eppnt->p_filesz) {
> -                    goto exit_perror;
> -                }
> -            }
> -            if (interp_name[eppnt->p_filesz - 1] != 0) {
> -                errmsg = "Invalid PT_INTERP entry";
> -                goto exit_errmsg;
> -            }
> -            *pinterp_name = interp_name;
>  #ifdef TARGET_MIPS
>          } else if (eppnt->p_type == PT_MIPS_ABIFLAGS) {
>              Mips_elf_abiflags_v0 abiflags;
>