linux-kernel - Re: [syzbot] [fs?] KASAN: slab-out-of-bounds Write in __put_unused

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Message-ID: <dlkmio7icps3j2l7iz5g7d2patw2ivssiaus7jzucbrqd4jaq5@w3rekecxeeka>
Date: Mon, 6 Jan 2025 12:15:15 +0100
From: Jan Kara <jack@...e.cz>
To: syzbot <syzbot+6a3aa63412255587b21b@...kaller.appspotmail.com>
Cc: amir73il@...il.com, jack@...e.cz, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, repnop@...gle.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [fs?] KASAN: slab-out-of-bounds Write in __put_unused_fd

On Tue 31-12-24 05:27:19, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8155b4ef3466 Add linux-next specific files for 20241220
> git tree:       linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=105ba818580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9c90bb7161a56c88
> dashboard link: https://syzkaller.appspot.com/bug?extid=6a3aa63412255587b21b
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10e670b0580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f42ac4580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/98a974fc662d/disk-8155b4ef.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/2dea9b72f624/vmlinux-8155b4ef.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/593a42b9eb34/bzImage-8155b4ef.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6a3aa63412255587b21b@...kaller.appspotmail.com
> 
> RAX: ffffffffffffffda RBX: 00007ffd163c2680 RCX: 00007f8b75a4d669
> RDX: 00007f8b75a4c8a0 RSI: 0000000000000000 RDI: 0000000000000008
> RBP: 0000000000000001 R08: 00007ffd163c2407 R09: 00000000000000a0
> R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
> R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> ==================================================================
> BUG: KASAN: use-after-free in instrument_write include/linux/instrumented.h:40 [inline]
> BUG: KASAN: use-after-free in ___clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:44 [inline]
> BUG: KASAN: use-after-free in __clear_open_fd fs/file.c:324 [inline]
> BUG: KASAN: use-after-free in __put_unused_fd+0xdb/0x2a0 fs/file.c:600
> Write of size 8 at addr ffff88804952aa48 by task syz-executor128/5830

Good catch. Thanks! Should be fixed now:

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next

									Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR