[syzbot] [bcachefs?] WARNING: kmalloc bug in __snapshot_t_mut

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c13320499ba0 Merge tag '6.10-rc-smb3-fixes-part2' of git:/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=14fb3ec8980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ee7b962709a5f5a5
dashboard link: https://syzkaller.appspot.com/bug?extid=770e99b65e26fa023ab1
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=157e822c980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ed3a3c980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/22adcef01567/disk-c1332049.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/03f224c81035/vmlinux-c1332049.xz
kernel image: https://storage.googleapis.com/syzbot-assets/711f192697c1/bzImage-c1332049.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/f94c66f22d99/mount_0.gz

The issue was bisected to:

commit f7643bc9749f270d487c32dc35b578575bf1adb0
Author: Kent Overstreet <kent.ov...@linux.dev>
Date: Wed Apr 17 05:26:02 2024 +0000

bcachefs: make btree read errors silent during scan

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1799b972980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1459b972980000
console output: https://syzkaller.appspot.com/x/log.txt?x=1059b972980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+770e99...@syzkaller.appspotmail.com
Fixes: f7643bc9749f ("bcachefs: make btree read errors silent during scan")

bcachefs (loop0): mounting version 1.7: mi_btree_bitmap opts=metadata_checksum=crc64,data_checksum=xxhash,compression=gzip,str_hash=crc64,nojournal_transaction_names
bcachefs (loop0): recovering from clean shutdown, journal seq 7
bcachefs (loop0): alloc_read... done
bcachefs (loop0): stripes_read... done
bcachefs (loop0): snapshots_read...
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5078 at mm/util.c:649 kvmalloc_node_noprof+0x17a/0x190 mm/util.c:649
Modules linked in:
CPU: 1 PID: 5078 Comm: syz-executor347 Not tainted 6.9.0-syzkaller-12398-gc13320499ba0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:kvmalloc_node_noprof+0x17a/0x190 mm/util.c:649
Code: cc 44 89 fe 81 e6 00 20 00 00 31 ff e8 6f 48 be ff 41 81 e7 00 20 00 00 74 0a e8 21 44 be ff e9 3b ff ff ff e8 17 44 be ff 90 <0f> 0b 90 e9 2d ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00
RSP: 0018:ffffc90004116c68 EFLAGS: 00010293
RAX: ffffffff81d7d179 RBX: 00000037ffc7c850 RCX: ffff88802d0d9e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff81d7d161 R09: 00000000ffffffff
R10: ffffc90004116b00 R11: fffff52000822d65 R12: ffffc90004116fef
R13: 00000000000100ff R14: 00000000ffffffff R15: 0000000000000000
FS: 000055557a8d2380(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005582515a4208 CR3: 0000000011274000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__snapshot_t_mut+0x3c/0x220 fs/bcachefs/snapshot.c:171
__bch2_mark_snapshot+0x130/0xac0 fs/bcachefs/snapshot.c:310
bch2_snapshots_read+0x596/0x1680 fs/bcachefs/snapshot.c:1845
bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:182
bch2_run_recovery_passes+0x19e/0x820 fs/bcachefs/recovery_passes.c:225
bch2_fs_recovery+0x2370/0x3720 fs/bcachefs/recovery.c:807
bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1031
bch2_fs_open+0xa8d/0xdf0 fs/bcachefs/super.c:2123
bch2_mount+0x71d/0x1310 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+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9cfdd8adea
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:00007ffdd812fab8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffdd812fad0 RCX: 00007f9cfdd8adea
RDX: 0000000020005d80 RSI: 0000000020005dc0 RDI: 00007ffdd812fad0
RBP: 0000000000000004 R08: 00007ffdd812fb10 R09: 0000000000005d64
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 00007ffdd812fb10 R14: 0000000000000003 R15: 0000000001000000
</TASK>


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***

Subject: WARNING: kmalloc bug in __snapshot_t_mut
Author: peil...@gmail.com

#syz test

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+770e99...@syzkaller.appspotmail.com

Tested on:

commit: 55027e68 Merge tag 'input-for-v6.10-rc5' of git://git...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10f3a389980000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf5def5af476d39a

dashboard link: https://syzkaller.appspot.com/bug?extid=770e99b65e26fa023ab1
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=170174c1980000

Note: testing is done by a robot and is best-effort only.