[syzbot] [bcachefs?] general protection fault in poll_state_synchronize_srcu

[syzbot <syzbot+3af9daea347788b15213@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2a8120d7b482 Merge tag 's390-6.10-2' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b5be58980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5dd4fde1337a9e18
dashboard link: https://syzkaller.appspot.com/bug?extid=3af9daea347788b15213
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-2a8120d7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/78c72ae6bdaf/vmlinux-2a8120d7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/99dbb805b738/bzImage-2a8120d7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3af9daea347788b15213@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000030: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000180-0x0000000000000187]
CPU: 0 PID: 111 Comm: kswapd0 Not tainted 6.9.0-syzkaller-10713-g2a8120d7b482 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:rcu_seq_done kernel/rcu/rcu.h:156 [inline]
RIP: 0010:poll_state_synchronize_srcu+0x43/0x90 kernel/rcu/srcutree.c:1543
Code: 48 83 ec 08 48 c1 ea 03 80 3c 02 00 75 45 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 38 48 8d bb 80 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 32 48 8b 93 80 01 00 00 31 c0 48 39 f2 78 0b f0 83
RSP: 0018:ffffc90000e6f698 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff888062204528
RDX: 0000000000000030 RSI: 0000000000000004 RDI: 0000000000000180
RBP: dffffc0000000000 R08: 0000000000000000 R09: fffffbfff283f87a
R10: ffffffff941fc3d7 R11: 0000000000000002 R12: ffff88804bca2cf0
R13: ffff88804bc3aec8 R14: ffff888062200000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88802c000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000f7f8cea0 CR3: 0000000045b60000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 bch2_btree_key_cache_scan+0x3c7/0x1820 fs/bcachefs/btree_key_cache.c:835
 do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
 shrink_slab+0x18a/0x1310 mm/shrinker.c:662
 shrink_one+0x493/0x7c0 mm/vmscan.c:4790
 shrink_many mm/vmscan.c:4851 [inline]
 lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4951
 shrink_node mm/vmscan.c:5910 [inline]
 kswapd_shrink_node mm/vmscan.c:6720 [inline]
 balance_pgdat+0x1105/0x1970 mm/vmscan.c:6911
 kswapd+0x5ea/0xbf0 mm/vmscan.c:7180
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:rcu_seq_done kernel/rcu/rcu.h:156 [inline]
RIP: 0010:poll_state_synchronize_srcu+0x43/0x90 kernel/rcu/srcutree.c:1543
Code: 48 83 ec 08 48 c1 ea 03 80 3c 02 00 75 45 48 b8 00 00 00 00 00 fc ff df 48 8b 5b 38 48 8d bb 80 01 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 32 48 8b 93 80 01 00 00 31 c0 48 39 f2 78 0b f0 83
RSP: 0018:ffffc90000e6f698 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff888062204528
RDX: 0000000000000030 RSI: 0000000000000004 RDI: 0000000000000180
RBP: dffffc0000000000 R08: 0000000000000000 R09: fffffbfff283f87a
R10: ffffffff941fc3d7 R11: 0000000000000002 R12: ffff88804bca2cf0
R13: ffff88804bc3aec8 R14: ffff888062200000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88802c100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbbf486e060 CR3: 0000000045a9e000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	48 83 ec 08          	sub    $0x8,%rsp
   4:	48 c1 ea 03          	shr    $0x3,%rdx
   8:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   c:	75 45                	jne    0x53
   e:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  15:	fc ff df
  18:	48 8b 5b 38          	mov    0x38(%rbx),%rbx
  1c:	48 8d bb 80 01 00 00 	lea    0x180(%rbx),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	75 32                	jne    0x62
  30:	48 8b 93 80 01 00 00 	mov    0x180(%rbx),%rdx
  37:	31 c0                	xor    %eax,%eax
  39:	48 39 f2             	cmp    %rsi,%rdx
  3c:	78 0b                	js     0x49
  3e:	f0                   	lock
  3f:	83                   	.byte 0x83


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