linux-kernel - next-20170515: WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236 note

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Date:   Tue, 16 May 2017 00:06:50 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Stephen Smalley <sds@...ho.nsa.gov>, Ingo Molnar <mingo@...nel.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Mateusz Guzik <mguzik@...hat.com>, mcgrof@...nel.org,
        linux-kernel@...r.kernel.org
Subject: next-20170515: WARNING: CPU: 0 PID: 1 at
 arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0

For a few kernel releases now I have managed to trigger the warning added via
commit e1a58320a38dfa ("x86/mm: Warn on W^X mappings", merged upstream since
v4.4) on my KVM qemu x86_64 system. Since I just booted into the shiny new
linux-next tag next-20170515 (based on v4.12-rc1) and this is still triggering
I figured its time to tackle this.

Let me know if this is already known or what can be done to try to fix this.

Using QEMU emulator version 2.7.94 (v2.8.0-rc4-dirty)

I will try updating my distro package for qemu and see if perhaps its this
and for the other odd fork issue I reported [0].

[0] https://lkml.kernel.org/r/CAB=NE6VZXq3y-3pfouYTBUco2Cq2xqoLZrgDFdVx+_=_=SwG_Q@mail.gmail.com

My config:

http://drvbp1.linux-foundation.org/~mcgrof/2017/05/15/configs/piggy-x86_64_qemu_fork_kmemleak.config

The splat:

[    0.911209] x86/mm: Found insecure W+X mapping at address ffffffffc0288000/0xffffffffc0288000
[    0.912066] ------------[ cut here ]------------
[    0.912544] WARNING: CPU: 0 PID: 1 at arch/x86/mm/dump_pagetables.c:236 note_page+0x630/0x7e0
[    0.913381] Modules linked in:
[    0.913672] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc1-next-20170515+ #144
[    0.914434] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.1-0-g8891697-prebuilt.qemu-project.org 04/01/2014
[    0.915595] task: ffff98d43a5eac80 task.stack: ffffad22c0630000
[    0.916174] RIP: 0010:note_page+0x630/0x7e0
[    0.916595] RSP: 0018:ffffad22c0633df0 EFLAGS: 00010286
[    0.917101] RAX: 0000000000000051 RBX: ffffad22c0633e88 RCX: ffffffff91256708
[    0.917805] RDX: 0000000000000000 RSI: 0000000000000096 RDI: 0000000000000246
[    0.918511] RBP: ffffad22c0633e28 R08: 6666666666666678 R09: 0000000000000160
[    0.919214] R10: ffffad22c0633dd8 R11: 3030303838323063 R12: 0000000000000000
[    0.919917] R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000
[    0.920615] FS:  0000000000000000(0000) GS:ffff98d43fc00000(0000) knlGS:0000000000000000
[    0.921384] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.921943] CR2: 0000000000000000 CR3: 00000000a3a09000 CR4: 00000000000006f0
[    0.922657] Call Trace:
[    0.922901]  ptdump_walk_pgd_level_core+0x3e7/0x490
[    0.923354]  ? 0xffffffff90600000
[    0.923662]  ptdump_walk_pgd_level_checkwx+0x17/0x20
[    0.924145]  mark_rodata_ro+0xf4/0x100
[    0.924536]  ? rest_init+0x80/0x80
[    0.924862]  kernel_init+0x2f/0x100
[    0.925197]  ret_from_fork+0x2c/0x40
[    0.925552] Code: 48 c7 43 28 00 00 00 00 48 89 43 20 e9 05 fd ff ff 48 8b 73 10 48 c7 c7 c8 34 fe 90 c6 05 c8 eb bc 00 01 48 89 f2 e8 8d fc 11 00 <0f> ff e9 1f fa ff ff 48 8b 70 20 48 c7 c7 05 b1 fe 90 e8 76 fc
[    0.927368] ---[ end trace 97137ae213b9cb25 ]---
[    0.927830] x86/mm: Checked W+X mappings: FAILED, 1 W+X pages found.

  Luis