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

[Philippe Mathieu-Daudé]

On 10/3/20 7:38 PM, Philippe Mathieu-Daudé wrote:
> 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)?

I just sent a patch using g_steal_pointer() instead:
https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg00792.html
(Maybe I should have tagged it RFC as this is the first
time I try this API).

> 
>> +                    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;
>>
> 
>