linux-kernel - Re: [tip: objtool/core] jump_label, x86: Allow short NOPs

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:   Tue, 29 Jun 2021 21:35:37 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org,
        linux-tip-commits@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        x86@...nel.org, masahiroy@...nel.org, michal.lkml@...kovi.net,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [tip: objtool/core] jump_label, x86: Allow short NOPs

On Tue, Jun 29, 2021 at 09:01:25PM +0100, Matthew Wilcox wrote:
> So this got merged without the corresponding Kbuild update being merged,
> and my kernel failed to boot.  Bisect got as far as
> 
> $ git bisect good
> Bisecting: 4 revisions left to test after this (roughly 2 steps)
> [ab3257042c26d0cd44793c741e2f89bf38b21fe8] jump_label, x86: Allow short NOPs
> 
> before my sluggish memory remembered this thread from six weeks ago.
> 
> So if anybody else hits this, do a make clean.

Actually, this is a different bug with the same symptom.

Applying the patch from Peter, and running it:

$ ./.build_test_kernel-x86_64/tools/objtool/objtool check -abdJsuld .build_test_kernel-x86_64/vmlinux.o
nr_sections: 15446
section_bits: 13
nr_symbols: 116448
symbol_bits: 16
max_reloc: 8031700
tot_reloc: 12477754
reloc_bits: 19
nr_insns: 2523443
.build_test_kernel-x86_64/vmlinux.o: warning: objtool: want_init_on_free()+0x0: jump-label unpatched

This is against a freshly built kernel -- i removed the build directory,
copied in a .config file and built a fresh kernel.