linux-kernel - Re: [GIT PULL] x86/asm changes for v5.6

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Date:   Thu, 30 Jan 2020 08:55:49 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Damian Tometzki <damian.tometzki@...ilie-tometzki.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Luck, Tony" <tony.luck@...el.com>, Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/asm changes for v5.6

Hello Damian,

On Thu, Jan 30, 2020 at 06:47:14AM +0100, Damian Tometzki wrote:
> in my qemu env the system isnt coming up. I tried both with and without the
> changes from Borislav.

in the future, please do not hijack the thread like that but start a new
one or open a bug on bugzilla.kernel.org. Your issue is something else.

> 0.605193] ------------[ cut here ]------------
> [    0.605933] General protection fault in user access. Non-canonical
> address?

There it is.

> [    0.605948] WARNING: CPU: 0 PID: 1 at arch/x86/mm/extable.c:77
> ex_handler_uaccess+0x48/0x50
> [    0.606931] Modules linked in:
> [    0.606931] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.5.0 #15
> [    0.606931] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
> [    0.606931] RIP: 0010:ex_handler_uaccess+0x48/0x50
> [    0.606931] Code: 83 c4 08 b8 01 00 00 00 5b c3 80 3d 78 75 50 01 00 75
> dc 48 c7 c7 00 ea 1e 82 48 89 34 24 c6 05 64 75 50 01 01 e8 9e fd 00 00 <0f>
> 0b 48 8b 34 24 eb bd 80 3d 4f 75 50 01 00 55 48 89 fd 53 49
> [    0.606931] RSP: 0000:ffffc900000dbc30 EFLAGS: 00010286
> [    0.606931] RAX: 000000000000003f RBX: ffffffff82339d6c RCX:
> 0000000000000000
> [    0.606931] RDX: 0000000000000007 RSI: ffffffff8316dc5f RDI:
> ffffffff8316e05f
> [    0.606931] RBP: 000000000000000d R08: ffffffff8316dc20 R09:
> 0000000000029840
> [    0.606931] R10: 000000010196fab4 R11: 0000000000000001 R12:
> 0000000000000000
> [    0.606931] R13: 0000000000000000 R14: 0000000000000000 R15:
> 0000000000000000
> [    0.606931] FS:  0000000000000000(0000) GS:ffff88800f800000(0000)
> knlGS:0000000000000000
> [    0.606931] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.606931] CR2: 0000000000000000 CR3: 000000000240a000 CR4:
> 00000000000006f0
> [    0.606931] Call Trace:
> [    0.606931]  fixup_exception+0x3e/0x51
> [    0.606931]  do_general_protection+0x9c/0x260
> [    0.606931]  general_protection+0x28/0x30
> [    0.606931] RIP: 0010:copy_user_generic_string+0x2c/0x40
> [    0.606931] Code: 00 83 fa 08 72 27 89 f9 83 e1 07 74 15 83 e9 08 f7 d9
> 29 ca 8a 06 88 07 48 ff c6 48 ff c7 ff c9 75 f2 89 d1 c1 e9 03 83 e2 07 <f3>
> 48 a5 89 d1 f3 a4 31 c0 0f 1f 00 c3 0f 1f 80 00 00 00 00 0f
> [    0.606931] RSP: 0000:ffffc900000dbda0 EFLAGS: 00010246
> [    0.606931] RAX: 0000000000000000 RBX: ffff88801e488000 RCX:
> 0000000000000001
> [    0.606931] RDX: 0000000000000000 RSI: 009896808086a201 RDI:
> ffffc900000dbdc0

It looks like dquot_init->register_sysctl_table-> ... does copy_to_user
at some point and it goes off into the weeds and %rsi becomes
non-canonical.

Please start a new thread or open a bug and upload your .config and
dmesg. We'll continue debugging that there.

Thx.

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Felix Imendörffer, HRB 36809, AG Nürnberg