[syzbot] [bcachefs?] WARNING in bch2_prt_printf

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 75fa778d74b7 Add linux-next specific files for 20240510
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13cb8b04980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ccdd3ebd6715749a
dashboard link: https://syzkaller.appspot.com/bug?extid=4e41a25632658c77b441
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=15f5ec3f180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=126cdfc0980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ad9391835bcf/disk-75fa778d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d827b3da9a26/vmlinux-75fa778d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f32f0182388/bzImage-75fa778d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/244f301e9090/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e41a2...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5100 at mm/page_alloc.c:4672 __alloc_pages_noprof+0x36a/0x6c0 mm/page_alloc.c:4672
Modules linked in:
CPU: 1 PID: 5100 Comm: syz-executor185 Not tainted 6.9.0-rc7-next-20240510-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:__alloc_pages_noprof+0x36a/0x6c0 mm/page_alloc.c:4672
Code: a9 00 00 08 00 0f 85 12 01 00 00 44 89 e9 81 e1 7f ff ff ff a9 00 00 04 00 44 0f 45 e9 e9 02 01 00 00 c6 05 c3 c3 a8 0d 01 90 <0f> 0b 90 83 fb 0a 0f 86 6c fd ff ff 45 31 ed 48 c7 44 24 20 0e 36
RSP: 0018:ffffc90002dd6940 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 000000000000000b RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc90002dd69c8
RBP: ffffc90002dd6a48 R08: ffffc90002dd69c7 R09: 0000000000000000
R10: ffffc90002dd69a0 R11: fffff520005bad39 R12: 1ffff920005bad30
R13: 0000000000040cc0 R14: dffffc0000000000 R15: 1ffff920005bad2c
FS: 0000555573a66380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055f740571f40 CR3: 0000000022430000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
__kmalloc_large_node+0x91/0x1f0 mm/slub.c:4066
__do_kmalloc_node mm/slub.c:4109 [inline]
kmalloc_node_track_caller_noprof+0x2d2/0x450 mm/slub.c:4141
__do_krealloc mm/slab_common.c:1183 [inline]
krealloc_noprof+0x7d/0x120 mm/slab_common.c:1216
bch2_printbuf_make_room fs/bcachefs/printbuf.c:52 [inline]
bch2_prt_printf+0x41e/0xa10 fs/bcachefs/printbuf.c:179
bch2_bkey_to_text+0x124/0x330 fs/bcachefs/bkey_methods.c:288
bch2_bkey_val_to_text+0x35/0x160 fs/bcachefs/bkey_methods.c:312
journal_entry_btree_keys_to_text+0x1d7/0x390 fs/bcachefs/journal_io.c:437
bch2_sb_clean_to_text+0x138/0x240 fs/bcachefs/sb-clean.c:313
bch2_sb_field_validate+0x201/0x2e0 fs/bcachefs/super-io.c:1234
bch2_sb_validate+0xa69/0xe00 fs/bcachefs/super-io.c:468
__bch2_read_super+0xc9a/0x1460 fs/bcachefs/super-io.c:822
bch2_fs_open+0x246/0xdf0 fs/bcachefs/super.c:2070
bch2_mount+0x71d/0x1320 fs/bcachefs/fs.c:1917
legacy_get_tree+0xee/0x190 fs/fs_context.c:662
vfs_get_tree+0x90/0x2a0 fs/super.c:1780
do_new_mount+0x2be/0xb40 fs/namespace.c:3352
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fce02323b3a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffc866b068 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffc866b080 RCX: 00007fce02323b3a
RDX: 0000000020000000 RSI: 0000000020011a40 RDI: 00007fffc866b080
RBP: 0000000000000004 R08: 00007fffc866b0c0 R09: 00000000000119f4
R10: 0000000001200014 R11: 0000000000000282 R12: 0000000001200014
R13: 00007fffc866b0c0 R14: 0000000000000003 R15: 0000000001000000
</TASK>


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[syzbot]

syzbot has bisected this issue to:

commit f39055220f6f98a180e3503fe05bbf9921c425c8
Author: Kent Overstreet <kent.ov...@linux.dev>
Date: Mon May 6 02:28:00 2024 +0000

bcachefs: Add missing validation for superblock section clean

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17a16504980000
start commit: 75fa778d74b7 Add linux-next specific files for 20240510
git tree: linux-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=14616504980000
console output: https://syzkaller.appspot.com/x/log.txt?x=10616504980000

kernel config: https://syzkaller.appspot.com/x/.config?x=ccdd3ebd6715749a
dashboard link: https://syzkaller.appspot.com/bug?extid=4e41a25632658c77b441

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15f5ec3f180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=126cdfc0980000

Reported-by: syzbot+4e41a2...@syzkaller.appspotmail.com
Fixes: f39055220f6f ("bcachefs: Add missing validation for superblock section clean")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Kent Overstreet]

Dmitry, I can't do anything with this one because you're using panic on
warn; if it had finished printing the buffer I could see what went
haywire.

Any chance you could change syzbot to just check for warnings/oopses
after the test finishes, like fstests does it?