lkml.org 
[lkml]   [2022]   [Aug]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 2/3] modpost: use more reliable way to get fromsec in section_rel(a)()
On Sat, Jul 30, 2022 at 10:37 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> The section name of Rel and Rela starts with ".rel" and ".rela"
> respectively (but, I do not know whether this is specification or
> convention).
>
> For example, ".rela.text" holds relocation entries applied to the
> ".text" section.
>
> So, the code chops the ".rel" or ".rela" prefix to get the name of
> the section to which the relocation applies.
>
> However, I do not like to skip 4 or 5 bytes blindly because it is
> potential memory overrun.
>
> The ELF specification provides a more reliable way to do this.
>
> - The sh_info field holds extra information, whose interpretation
> depends on the section type
>
> - If the section type is SHT_REL or SHT_RELA, the sh_info field holds
> the section header index of the section to which the relocation
> applies.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Yes, this seems much safer; thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>
> scripts/mod/modpost.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 148b38699889..c6a055c0291e 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1723,8 +1723,7 @@ static void section_rela(const char *modname, struct elf_info *elf,
> Elf_Rela *start = (void *)elf->hdr + sechdr->sh_offset;
> Elf_Rela *stop = (void *)start + sechdr->sh_size;
>
> - fromsec = sech_name(elf, sechdr);
> - fromsec += strlen(".rela");
> + fromsec = sec_name(elf, sechdr->sh_info);
> /* if from section (name) is know good then skip it */
> if (match(fromsec, section_white_list))
> return;
> @@ -1776,8 +1775,7 @@ static void section_rel(const char *modname, struct elf_info *elf,
> Elf_Rel *start = (void *)elf->hdr + sechdr->sh_offset;
> Elf_Rel *stop = (void *)start + sechdr->sh_size;
>
> - fromsec = sech_name(elf, sechdr);
> - fromsec += strlen(".rel");
> + fromsec = sec_name(elf, sechdr->sh_info);
> /* if from section (name) is know good then skip it */
> if (match(fromsec, section_white_list))
> return;
> --
> 2.34.1
>


--
Thanks,
~Nick Desaulniers

\
 
 \ /
  Last update: 2022-08-02 19:59    [W:0.133 / U:0.264 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site