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Message-ID: <zdzdhxenl7vdnu6wfm22r7liaejsdgfljoodwbpcpj7zb4dzet@g6fdggigssse>
Date: Wed, 9 Apr 2025 17:51:22 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Charalampos Mitrodimas <charmitro@...teo.net>
Cc: syzbot <syzbot+aec9606169fbc3a12ca6@...kaller.appspotmail.com>,
linux-bcachefs@...r.kernel.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free
On Wed, Apr 09, 2025 at 04:09:41PM +0000, Charalampos Mitrodimas wrote:
> syzbot <syzbot+aec9606169fbc3a12ca6@...kaller.appspotmail.com> writes:
>
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: a4cda136f021 Add linux-next specific files for 20250404
> > git tree: linux-next
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=12c3db4c580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=8a257c454bb1afb7
> > dashboard link: https://syzkaller.appspot.com/bug?extid=aec9606169fbc3a12ca6
> > 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=17ca0c04580000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11c3db4c580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/59048bc9c206/disk-a4cda136.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/ad2ba7306f20/vmlinux-a4cda136.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/b3bef7acbf10/bzImage-a4cda136.xz
> > mounted in repro: https://storage.googleapis.com/syzbot-assets/110624be1513/mount_0.gz
> >
> > The issue was bisected to:
> >
> > commit dcffc3b1ae3251d796a25c673f614e3099ca83d3
> > Author: Kent Overstreet <kent.overstreet@...ux.dev>
> > Date: Sun Mar 30 03:11:08 2025 +0000
> >
> > bcachefs: Split up bch_dev.io_ref
> >
> > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13948c04580000
> > final oops: https://syzkaller.appspot.com/x/report.txt?x=10548c04580000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=17948c04580000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+aec9606169fbc3a12ca6@...kaller.appspotmail.com
> > Fixes: dcffc3b1ae32 ("bcachefs: Split up bch_dev.io_ref")
> >
> > bcachefs (loop0): shutting down
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 5844 at fs/bcachefs/super.c:1229 bch2_dev_free+0x228/0x290 fs/bcachefs/super.c:1229
> > Modules linked in:
> > CPU: 0 UID: 0 PID: 5844 Comm: syz-executor121 Not tainted 6.14.0-next-20250404-syzkaller #0 PREEMPT(full)
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> > RIP: 0010:bch2_dev_free+0x228/0x290 fs/bcachefs/super.c:1229
> > Code: ff e8 4c cf 74 00 4c 89 ef e8 44 cf 74 00 48 89 df 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d e9 ee 53 96 07 e8 59 e9 32 fd 90 <0f> 0b 90 e9 09 fe ff ff e8 4b e9 32 fd 90 0f 0b 90 e9 15 fe ff ff
> > RSP: 0018:ffffc9000406fb88 EFLAGS: 00010293
> > RAX: ffffffff849073d7 RBX: ffff888035282000 RCX: ffff888034af9e00
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > RBP: ffff8880352820c0 R08: ffffffff850552f7 R09: 0000000000000000
> > R10: ffff888035282208 R11: ffffed1006a5044a R12: ffff888075e003f0
> > R13: ffff8880352820b0 R14: ffff888075e00000 R15: ffff888075e007b2
> > FS: 000055558bb20380(0000) GS:ffff888124f8f000(0000) knlGS:0000000000000000
> > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 000000000045bdd0 CR3: 00000000122a0000 CR4: 00000000003526f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> > <TASK>
> > bch2_fs_free+0x2b0/0x400 fs/bcachefs/super.c:688
> > deactivate_locked_super+0xc4/0x130 fs/super.c:473
> > cleanup_mnt+0x422/0x4c0 fs/namespace.c:1435
> > task_work_run+0x251/0x310 kernel/task_work.c:227
> > ptrace_notify+0x2dc/0x390 kernel/signal.c:2520
> > ptrace_report_syscall include/linux/ptrace.h:415 [inline]
> > ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
> > syscall_exit_work+0xc7/0x1d0 kernel/entry/common.c:173
> > syscall_exit_to_user_mode_prepare kernel/entry/common.c:200 [inline]
> > __syscall_exit_to_user_mode_work kernel/entry/common.c:205 [inline]
> > syscall_exit_to_user_mode+0x24a/0x340 kernel/entry/common.c:218
> > do_syscall_64+0x100/0x230 arch/x86/entry/syscall_64.c:100
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f49b0cec447
> > Code: 07 00 48 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8
> > RSP: 002b:00007ffd94723978 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
> > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f49b0cec447
> > RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffd94723a30
> > RBP: 00007ffd94723a30 R08: 0000000000000000 R09: 0000000000000000
> > R10: 00000000ffffffff R11: 0000000000000206 R12: 00007ffd94724aa0
> > R13: 000055558bb216c0 R14: 0000000000000001 R15: 431bde82d7b634db
> > </TASK>
> >
> >
> > ---
>
> #syz test
>
> From: Charalampos Mitrodimas <charmitro@...teo.net>
> Subject: [PATCH] bcachefs: Fix WARN_ON in bch2_dev_free
>
> After splitting bch_dev.io_ref into separate READ and WRITE refs, we
> need to ensure both refs are properly stopped before freeing a device.
> Add bch2_dev_io_ref_stop(ca, WRITE) to bch2_fs_free() to prevent the
> WARNING in bch2_dev_free().
>
> Reported-by: syzbot+aec9606169fbc3a12ca6@...kaller.appspotmail.com
> Fixes: dcffc3b1ae32 ("bcachefs: Split up bch_dev.io_ref")
> Signed-off-by: Charalampos Mitrodimas <charmitro@...teo.net>
> ---
> fs/bcachefs/super.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
> index a58edde43bee..089b69b685d9 100644
> --- a/fs/bcachefs/super.c
> +++ b/fs/bcachefs/super.c
> @@ -684,6 +684,7 @@ void bch2_fs_free(struct bch_fs *c)
> if (ca) {
> EBUG_ON(atomic_long_read(&ca->ref) != 1);
> bch2_dev_io_ref_stop(ca, READ);
> + bch2_dev_io_ref_stop(ca, WRITE);
> bch2_free_super(&ca->disk_sb);
> bch2_dev_free(ca);
> }
> --
> 2.39.5
>
This would seem to indicate shutting down without going read-only, there
might be a deeper bug here
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