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Message-ID: <202308181030.0DA3FD14@keescook>
Date: Fri, 18 Aug 2023 10:33:26 -0700
From: Kees Cook <keescook@...omium.org>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: syzbot <syzbot+6ec38f7a8db3b3fb1002@...kaller.appspotmail.com>,
anton@...era.com, brauner@...nel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-ntfs-dev@...ts.sourceforge.net,
syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: Re: [syzbot] [ntfs?] WARNING in do_open_execat
On Fri, Aug 18, 2023 at 11:26:51AM -0500, Eric W. Biederman wrote:
> syzbot <syzbot+6ec38f7a8db3b3fb1002@...kaller.appspotmail.com> writes:
>
> > Hello,
> >
> > syzbot found the following issue on:
>
> Not an issue.
> Nothing to do with ntfs.
>
> The code is working as designed and intended.
>
> syzbot generated a malformed exec and the kernel made it
> well formed and warned about it.
>
> Human beings who run syzbot please mark this as not an issue in your
> system. The directions don't have a way to say that the code is working
> as expected and designed.
WARN and BUG should not be reachable from userspace, so if this can be
tripped we should take a closer look and likely fix it...
> > HEAD commit: 16931859a650 Merge tag 'nfsd-6.5-4' of git://git.kernel.or..
> > git tree: upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=13e2673da80000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=aa796b6080b04102
> > dashboard link: https://syzkaller.appspot.com/bug?extid=6ec38f7a8db3b3fb1002
> > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17cdbc65a80000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1262d8cfa80000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/eecc010800b4/disk-16931859.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/f45ae06377a7/vmlinux-16931859.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/68891896edba/bzImage-16931859.xz
> > mounted in repro: https://storage.googleapis.com/syzbot-assets/4b6ab78b223a/mount_0.gz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+6ec38f7a8db3b3fb1002@...kaller.appspotmail.com
> >
> > ntfs: volume version 3.1.
> > process 'syz-executor300' launched './file1' with NULL argv: empty string added
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 5020 at fs/exec.c:933 do_open_execat+0x18f/0x3f0 fs/exec.c:933
This is a double-check I left in place, since it shouldn't have been reachable:
/*
* may_open() has already checked for this, so it should be
* impossible to trip now. But we need to be extra cautious
* and check again at the very end too.
*/
err = -EACCES;
if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode) ||
path_noexec(&file->f_path)))
goto exit;
So yes, let's figure this out...
--
Kees Cook
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