linux-kernel - Re: [syzbot] general protection fault in mpol_parse

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Message-Id: <20221031160553.5afd9c461ebf34cfdcf70881@linux-foundation.org>
Date:   Mon, 31 Oct 2022 16:05:53 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+a7f196a1dbf5e2c70568@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com, Mike Rapoport <rppt@...nel.org>
Subject: Re: [syzbot] general protection fault in mpol_parse_str

On Sun, 30 Oct 2022 12:57:43 -0700 syzbot <syzbot+a7f196a1dbf5e2c70568@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    4d48f589d294 Add linux-next specific files for 20221021

Thanks.

> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=165e12da880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2c4b7d600a5739a6
> dashboard link: https://syzkaller.appspot.com/bug?extid=a7f196a1dbf5e2c70568
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f10ff6880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=145f1ff2880000

does

	memcpy((void*)0x20000100, "mpol=", 5);
	syscall(__NR_mount, 0ul, 0x20000040ul, 0x20000080ul, 0ul, 0x20000100ul);

so I assume we've fallen afoul of the patch "vfs: parse: deal with zero
length string value"
(https://lkml.kernel.org/r/166365878918.39016.12757946948158123324.stgit@donald.themaw.net).

I have dropped that patch today so hopefully we're all good now.

>
> ...
>