linux-kernel - Re: [syzbot] KASAN: null-ptr-deref Read in filp

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Message-ID: <20210714135756.ammzl2vfiepzg3ve@wittgenstein>
Date:   Wed, 14 Jul 2021 15:57:56 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     syzbot <syzbot+283ce5a46486d6acdbaf@...kaller.appspotmail.com>
Cc:     brauner@...nel.org, dvyukov@...gle.com, gregkh@...uxfoundation.org,
        gscrivan@...hat.com, hch@....de, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable-commits@...r.kernel.org,
        stable@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        torvalds@...ux-foundation.org, viro@...iv.linux.org.uk
Subject: Re: [syzbot] KASAN: null-ptr-deref Read in filp_close (2)

On Wed, Jul 14, 2021 at 03:51:57PM +0200, Christian Brauner wrote:
> On Mon, Jul 12, 2021 at 09:12:20PM -0700, syzbot wrote:
> > syzbot has found a reproducer for the following issue on:
> > 
> > HEAD commit:    7fef2edf sd: don't mess with SD_MINORS for CONFIG_DEBUG_BL..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=178919b0300000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=20276914ec6ad813
> > dashboard link: https://syzkaller.appspot.com/bug?extid=283ce5a46486d6acdbaf
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=120220f2300000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=115f37b4300000
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+283ce5a46486d6acdbaf@...kaller.appspotmail.com
> > 
> > ==================================================================
> > BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
> > BUG: KASAN: use-after-free in atomic64_read include/asm-generic/atomic-instrumented.h:605 [inline]
> > BUG: KASAN: use-after-free in atomic_long_read include/asm-generic/atomic-long.h:29 [inline]
> > BUG: KASAN: use-after-free in filp_close+0x22/0x170 fs/open.c:1306
> > Read of size 8 at addr ffff888025a40a78 by task syz-executor493/8445
> 
> #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/ 595fac5cecba71935450ec431eb8dfa963cf45fe 

Hm, git.kernel.org doesn't seem to have caught up. Let's try:

#syz test: https://gitlab.com/brauner/linux.git 595fac5cecba71935450ec431eb8dfa963cf45fe