[syzbot] [bcachefs?] WARNING in bch2_dev_free

[syzbot] [bcachefs?] WARNING in bch2_dev_free

[syzbot]

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@linux.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@syzkaller.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>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free

[Charalampos Mitrodimas]

syzbot <syzbot+aec9606169fbc3a12ca6@syzkaller.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@linux.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@syzkaller.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@posteo.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@syzkaller.appspotmail.com
Fixes: dcffc3b1ae32 ("bcachefs: Split up bch_dev.io_ref")
Signed-off-by: Charalampos Mitrodimas <charmitro@posteo.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

Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for batadv0 to become free. Usage count = 3


Tested on:

commit:         a2458824 Merge tag 'linux_kselftest-kunit-6.15-rc2' of..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153ffb4c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fb8650d88e9fb80f
dashboard link: https://syzkaller.appspot.com/bug?extid=aec9606169fbc3a12ca6
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17b7fb4c580000

Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free

[Kent Overstreet]

On Wed, Apr 09, 2025 at 04:09:41PM +0000, Charalampos Mitrodimas wrote:
> syzbot <syzbot+aec9606169fbc3a12ca6@syzkaller.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@linux.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@syzkaller.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@posteo.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@syzkaller.appspotmail.com
> Fixes: dcffc3b1ae32 ("bcachefs: Split up bch_dev.io_ref")
> Signed-off-by: Charalampos Mitrodimas <charmitro@posteo.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

Re: [syzbot] #syz test

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: #syz test
Author: gshahrouzi@gmail.com

Try to remove device but fails
Reinitialize reference counting for write operations for device
Shut down the filesystem
Make the filesystem read only
	Read-write bit is not set so it skips trying to make the filesystem read-only, implying that the filesystem is already in read-only mode.
Encounter error because write operations are still assigned to a device
When the filesystem is starting up, it tries setting it to set the filesystem to read-only but it’s already set.
When failing to remove a device, it tries giving back write permissions to a device when the filesystem is read-only (not sure if this is nonsensical or not).
Since a device has write permissions, it tries to remove them but fails because the filesystem is in read-only mode.
So the fix here is to prevent it from giving the device write permissions if the filesystem is in read-only mode.

Signed-off-by: Gabriel Shahrouzi <gshahrouzi@gmail.com>
---
 fs/bcachefs/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index b79e80a435e09..788e870bfef6a 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -1757,7 +1757,8 @@ int bch2_dev_remove(struct bch_fs *c, struct bch_dev *ca, int flags)
 	up_write(&c->state_lock);
 	return 0;
 err:
-	if (ca->mi.state == BCH_MEMBER_STATE_rw &&
+	if (test_bit(BCH_FS_rw, &c->flags) &&
+	    ca->mi.state == BCH_MEMBER_STATE_rw &&
 	    !percpu_ref_is_zero(&ca->io_ref[READ]))
 		__bch2_dev_read_write(c, ca);
 	up_write(&c->state_lock);
-- 
2.43.0

Re: [syzbot] #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5fc31936081919a8572a3d644f3fbb258038f337

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 5fc31936081919a8572a3d644f3fbb258038f337
Author: gshahrouzi@gmail.com

Another test with earlier branch because of unassociated error popping up:
unregister_netdevice: waiting for batadv0 to become free. Usage count = 3.

Signed-off-by: Gabriel Shahrouzi <gshahrouzi@gmail.com>
---
 fs/bcachefs/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index b79e80a435e09..788e870bfef6a 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -1757,7 +1757,8 @@ int bch2_dev_remove(struct bch_fs *c, struct bch_dev *ca, int flags)
 	up_write(&c->state_lock);
 	return 0;
 err:
-	if (ca->mi.state == BCH_MEMBER_STATE_rw &&
+	if (test_bit(BCH_FS_rw, &c->flags) &&
+	    ca->mi.state == BCH_MEMBER_STATE_rw &&
 	    !percpu_ref_is_zero(&ca->io_ref[READ]))
 		__bch2_dev_read_write(c, ca);
 	up_write(&c->state_lock);
-- 
2.43.0

Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for batadv0 to become free. Usage count = 3


Tested on:

commit:         ecd5d67a Merge tag 'pwm/for-6.15-rc2-fixes' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12e4ca3f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fb8650d88e9fb80f
dashboard link: https://syzkaller.appspot.com/bug?extid=aec9606169fbc3a12ca6
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11245c04580000

Re: [syzbot] [bcachefs?] WARNING in bch2_dev_free

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file fs/bcachefs/super.c
Hunk #1 FAILED at 1757.
1 out of 1 hunk FAILED



Tested on:

commit:         5fc31936 Merge tag 'net-6.14-rc8' of git://git.kernel...
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=bae073f4634b7fd
dashboard link: https://syzkaller.appspot.com/bug?extid=aec9606169fbc3a12ca6
compiler:       
patch:          https://syzkaller.appspot.com/x/patch.diff?x=12f21f4c580000

Re: [syzbot]

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: 
Author: kent.overstreet@linux.dev

#syz fix: bcachefs: Prevent granting write refs when filesystem is read-only