From: hpa@zytor.com
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Kees Cook <keescook@chromium.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Thomas Lendacky <Thomas.Lendacky@amd.com>,
Mauro Rossi <issor.oruam@gmail.com>, Michael Matz <matz@suse.de>
Subject: Re: [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils
Date: Mon, 13 Jan 2020 21:05:05 -0800 [thread overview]
Message-ID: <F7B2A25D-E6A2-4637-9802-8AEC543916E9@zytor.com> (raw)
In-Reply-To: <20200114035858.GA2536335@rani.riverdale.lan>
On January 13, 2020 7:58:59 PM PST, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>On Mon, Jan 13, 2020 at 05:57:23PM -0800, H. Peter Anvin wrote:
>> On 2020-01-13 17:53, Kees Cook wrote:>>
>> >> diff --git a/arch/x86/kernel/vmlinux.lds.S
>b/arch/x86/kernel/vmlinux.lds.S
>> >> index 3a1a819da137..bad4e22384dc 100644
>> >> --- a/arch/x86/kernel/vmlinux.lds.S
>> >> +++ b/arch/x86/kernel/vmlinux.lds.S
>> >> @@ -144,10 +144,12 @@ SECTIONS
>> >> *(.text.__x86.indirect_thunk)
>> >> __indirect_thunk_end = .;
>> >> #endif
>> >> +
>> >> + /* End of text section */
>> >> + _etext = .;
>> >> } :text =0xcccc
>> >>
>> >> - /* End of text section, which should occupy whole number of
>pages */
>> >> - _etext = .;
>> >> + /* .text should occupy whole number of pages */
>> >> . = ALIGN(PAGE_SIZE);
>> >
>> > NAK: linkers can add things at the end of .text that will go
>missing from
>> > the kernel if _etext isn't _outside_ the .text section, truly
>beyond the
>> > end of the .text section. This patch will break Control Flow
>Integrity
>> > checking since the jump tables are at the end of .text.
>> >
>> > Boris, we're always working around weird linker problems; I don't
>see a
>> > problem with the v2 patch to fix up old binutils...
>> >
>>
>> Why not add the marker into a separate section instead of leaving it
>as an
>> absolute "floater"? Very old binutils would botch that case, but I
>think that
>> has been long since addressed well below our current minimum version.
>>
>> -hpa
>>
>>
>>
>
>Kees, thanks, I noted in the other email that you had mentioned this in
>a since-reverted commit, but you did not mention in the most recent
>commit.
>
>hpa, I think this runs afoul of the bug you noted in commit
>fd952815307f
>("x86-32, relocs: Whitelist more symbols for ld bug workaround"), ld
>version 2.22.52.0.[12] can incorrectly promote relative symbols to
>absolute, if the output section they appear in is otherwise empty.
>
>That's 2.22, which is more recent than the 2.21 that the kernel
>documents as supported.
Oh right... they introduced that little piece of drain bramage.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2020-01-14 5:05 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 20:23 [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL Arvind Sankar
2020-01-10 20:38 ` Borislav Petkov
2020-01-10 20:50 ` Arvind Sankar
2020-01-10 21:50 ` [PATCH v2] " Arvind Sankar
2020-01-10 21:52 ` Arvind Sankar
2020-01-11 13:02 ` [PATCH] " Borislav Petkov
2020-01-11 17:20 ` Arvind Sankar
2020-01-11 17:32 ` Arvind Sankar
2020-01-13 13:43 ` Borislav Petkov
2020-01-13 16:13 ` Arvind Sankar
2020-01-13 16:38 ` Borislav Petkov
2020-01-13 17:59 ` Arvind Sankar
2020-01-13 18:08 ` Borislav Petkov
2020-01-14 4:17 ` Arvind Sankar
2020-01-14 11:25 ` Borislav Petkov
2020-01-14 16:32 ` Arvind Sankar
2020-01-14 4:08 ` Arvind Sankar
2020-01-13 19:53 ` [PATCH v3] x86/vmlinux: Fix vmlinux.lds.S with pre-2.23 binutils Arvind Sankar
2020-01-13 21:46 ` Tom Lendacky
2020-01-13 23:06 ` Arvind Sankar
2020-01-14 1:53 ` Kees Cook
2020-01-14 1:57 ` H. Peter Anvin
2020-01-14 2:20 ` Kees Cook
2020-01-14 3:58 ` Arvind Sankar
2020-01-14 5:05 ` hpa [this message]
2020-01-14 16:51 ` Borislav Petkov
2020-01-14 21:50 ` hpa
2020-01-15 0:21 ` Arvind Sankar
2020-01-15 12:24 ` Borislav Petkov
2020-03-16 16:02 ` [PATCH] Documentation/changes: Raise minimum supported binutils version to 2.23 Borislav Petkov
2020-03-16 20:54 ` Kees Cook
2020-03-23 20:44 ` Jason A. Donenfeld
2020-03-23 20:51 ` Kees Cook
2020-03-23 21:11 ` Jason A. Donenfeld
2020-03-25 17:33 ` David Laight
2020-03-24 9:02 ` Masahiro Yamada
2020-03-24 9:12 ` Masahiro Yamada
2020-03-24 15:38 ` Arvind Sankar
2020-03-24 17:31 ` Masahiro Yamada
2020-03-24 21:36 ` Arvind Sankar
2020-03-24 9:14 ` Borislav Petkov
2020-03-24 9:40 ` Masahiro Yamada
2020-03-24 12:00 ` Borislav Petkov
2020-03-24 16:22 ` Jason A. Donenfeld
2020-03-24 16:28 ` Borislav Petkov
2020-03-24 16:37 ` Linus Torvalds
2020-03-24 16:48 ` Borislav Petkov
2020-03-24 21:42 ` Arvind Sankar
2020-03-24 22:01 ` Arvind Sankar
2020-03-24 22:14 ` Linus Torvalds
2020-03-24 23:49 ` Arvind Sankar
2020-03-24 17:53 ` Kees Cook
2020-03-23 20:50 ` [PATCH] Documentation/changes: Raise minimum supported binutilsa " Nick Desaulniers
2020-01-13 23:38 ` [PATCH] x86/tools/relocs: Add _etext and __end_of_kernel_reserve to S_REL Arvind Sankar
2020-01-10 20:56 ` Kees Cook
[not found] ` <CAEQFVGa4fksPRtiLtBckSgbJY_JSHr07hoy5+5w-pAYym16YVg@mail.gmail.com>
2020-01-11 19:40 ` Fwd: " Mauro Rossi
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