linux-kernel - Re: [PATCH 5.18 13/70] objtool: skip non-text sections when adding return-thunk sites

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 25 Jul 2022 07:44:08 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bpetkov@...e.de>
Subject: Re: [PATCH 5.18 13/70] objtool: skip non-text sections when adding
 return-thunk sites

Hi,

I wonder, why this is needed in stable and not mainline?

Isn't this a different (non-upstream) dup of
951ddecf4356 objtool: Treat .text.__x86.* as noinstr
? (That is included in this release too.)

On 22. 07. 22, 11:07, Greg Kroah-Hartman wrote:
> From: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
> 
> The .discard.text section is added in order to reserve BRK, with a
> temporary function just so it can give it a size. This adds a relocation to
> the return thunk, which objtool will add to the .return_sites section.
> Linking will then fail as there are references to the .discard.text
> section.
> 
> Do not add instructions from non-text sections to the list of return thunk
> calls, avoiding the reference to .discard.text.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
> Acked-by: Josh Poimboeuf <jpoimboe@...nel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>   tools/objtool/check.c |    4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -1308,7 +1308,9 @@ static void add_return_call(struct objto
>   	insn->type = INSN_RETURN;
>   	insn->retpoline_safe = true;
>   
> -	list_add_tail(&insn->call_node, &file->return_thunk_list);
> +	/* Skip the non-text sections, specially .discard ones */
> +	if (insn->sec->text)
> +		list_add_tail(&insn->call_node, &file->return_thunk_list);
>   }
>   
>   static bool same_function(struct instruction *insn1, struct instruction *insn2)
> 
> 

thanks,
-- 
js
suse labs