syzbot


BUG: unable to handle kernel paging request in srcu_gp_start_if_needed

Status: moderation: reported on 2025/07/26 02:32
Subsystems: bcachefs
[Documentation on labels]
Reported-by: syzbot+42e30261e5a50e1e2e06@syzkaller.appspotmail.com
First crash: 35d, last: 35d
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream general protection fault in srcu_gp_start_if_needed (2) kernel 2 1 147d 143d 0/29 auto-obsoleted due to no activity on 2025/06/30 10:03
upstream KASAN: global-out-of-bounds Read in srcu_gp_start_if_needed bcachefs 17 1 460d 456d 27/29 fixed on 2024/08/23 03:09
upstream general protection fault in srcu_gp_start_if_needed kernel 2 1 250d 246d 0/29 auto-obsoleted due to no activity on 2025/02/16 21:52

Sample crash report:
bcachefs (loop3): Using encoding defined by superblock: utf8-12.1.0
bcachefs (loop3): initializing new filesystem
bcachefs (loop3): going read-write
bcachefs (loop3): marking superblocks
BUG: unable to handle page fault for address: ffffffff9cab6b98
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD df3d067 P4D df3d067 PUD df3e063 PMD 0 
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 6122 Comm: syz.3.23 Not tainted 6.16.0-rc7-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:227 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:239 [inline]
RIP: 0010:_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:142 [inline]
RIP: 0010:__lock_acquire+0x6c1/0xd20 kernel/locking/lockdep.c:5210
Code: b3 00 00 00 4c 89 f6 ba 08 00 00 00 e8 88 25 00 00 45 31 ff 85 c0 0f 84 f5 05 00 00 83 3d f6 8e 09 18 00 75 13 48 63 44 24 20 <48> 0f a3 05 87 ff 05 12 0f 83 15 05 00 00 31 ed 48 8b 3c 24 4c 8b
RSP: 0018:ffffc9000b72e4f8 EFLAGS: 00010046
RAX: 00000000483940f2 RBX: 0000000000000002 RCX: ffffffff93460000
RDX: 0000000000000008 RSI: ffff8880315c2990 RDI: ffff8880315c1e00
RBP: 00000000000000f2 R08: 0000000000000000 R09: ffffffff81a6c3cf
R10: dffffc0000000000 R11: fffff520016e5cb4 R12: 0000000000008000
R13: 0000000000000000 R14: ffff8880315c2990 R15: 0000000000000000
FS:  00007f80527ee6c0(0000) GS:ffff888125d57000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff9cab6b98 CR3: 0000000031f4e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 __raw_spin_trylock include/linux/spinlock_api_smp.h:90 [inline]
 _raw_spin_trylock+0x47/0x80 kernel/locking/spinlock.c:138
 spin_lock_irqsave_sdp_contention kernel/rcu/srcutree.c:375 [inline]
 srcu_gp_start_if_needed+0x31f/0x11d0 kernel/rcu/srcutree.c:1275
 __rcu_pending_enqueue fs/bcachefs/rcu_pending.c:498 [inline]
 rcu_pending_enqueue+0x729/0x880 fs/bcachefs/rcu_pending.c:531
 bkey_cached_free_noassert fs/bcachefs/btree_key_cache.c:115 [inline]
 bkey_cached_free+0x13a/0x1d0 fs/bcachefs/btree_key_cache.c:129
 bch2_btree_key_cache_drop+0x12b/0x7d0 fs/bcachefs/btree_key_cache.c:637
 bch2_trans_commit_write_locked fs/bcachefs/btree_trans_commit.c:785 [inline]
 do_bch2_trans_commit fs/bcachefs/btree_trans_commit.c:854 [inline]
 __bch2_trans_commit+0x7463/0x8870 fs/bcachefs/btree_trans_commit.c:1085
 bch2_trans_commit fs/bcachefs/btree_update.h:241 [inline]
 bch2_trans_mark_metadata_bucket+0x566/0x1260 fs/bcachefs/buckets.c:1091
 bch2_trans_mark_metadata_sectors fs/bcachefs/buckets.c:1108 [inline]
 __bch2_trans_mark_dev_sb fs/bcachefs/buckets.c:1148 [inline]
 bch2_trans_mark_dev_sb+0x3ed/0x7c0 fs/bcachefs/buckets.c:1176
 bch2_trans_mark_dev_sbs_flags+0x49c/0x500 fs/bcachefs/buckets.c:1186
 bch2_fs_initialize+0xd47/0x1550 fs/bcachefs/recovery.c:1235
 bch2_fs_start+0xaa0/0xda0 fs/bcachefs/super.c:1214
 bch2_fs_get_tree+0xb39/0x1520 fs/bcachefs/fs.c:2488
 vfs_get_tree+0x92/0x2b0 fs/super.c:1804
 do_new_mount+0x24a/0xa40 fs/namespace.c:3902
 do_mount fs/namespace.c:4239 [inline]
 __do_sys_mount fs/namespace.c:4450 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f805199014a
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f80527ede68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f80527edef0 RCX: 00007f805199014a
RDX: 0000200000000140 RSI: 0000200000000000 RDI: 00007f80527edeb0
RBP: 0000200000000140 R08: 00007f80527edef0 R09: 0000000000200414
R10: 0000000000200414 R11: 0000000000000246 R12: 0000200000000000
R13: 00007f80527edeb0 R14: 0000000000005ad0 R15: 0000200000000400
 </TASK>
Modules linked in:
CR2: ffffffff9cab6b98
---[ end trace 0000000000000000 ]---
RIP: 0010:variable_test_bit arch/x86/include/asm/bitops.h:227 [inline]
RIP: 0010:arch_test_bit arch/x86/include/asm/bitops.h:239 [inline]
RIP: 0010:_test_bit include/asm-generic/bitops/instrumented-non-atomic.h:142 [inline]
RIP: 0010:__lock_acquire+0x6c1/0xd20 kernel/locking/lockdep.c:5210
Code: b3 00 00 00 4c 89 f6 ba 08 00 00 00 e8 88 25 00 00 45 31 ff 85 c0 0f 84 f5 05 00 00 83 3d f6 8e 09 18 00 75 13 48 63 44 24 20 <48> 0f a3 05 87 ff 05 12 0f 83 15 05 00 00 31 ed 48 8b 3c 24 4c 8b
RSP: 0018:ffffc9000b72e4f8 EFLAGS: 00010046
RAX: 00000000483940f2 RBX: 0000000000000002 RCX: ffffffff93460000
RDX: 0000000000000008 RSI: ffff8880315c2990 RDI: ffff8880315c1e00
RBP: 00000000000000f2 R08: 0000000000000000 R09: ffffffff81a6c3cf
R10: dffffc0000000000 R11: fffff520016e5cb4 R12: 0000000000008000
R13: 0000000000000000 R14: ffff8880315c2990 R15: 0000000000000000
FS:  00007f80527ee6c0(0000) GS:ffff888125d57000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffff9cab6b98 CR3: 0000000031f4e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	b3 00                	mov    $0x0,%bl
   2:	00 00                	add    %al,(%rax)
   4:	4c 89 f6             	mov    %r14,%rsi
   7:	ba 08 00 00 00       	mov    $0x8,%edx
   c:	e8 88 25 00 00       	call   0x2599
  11:	45 31 ff             	xor    %r15d,%r15d
  14:	85 c0                	test   %eax,%eax
  16:	0f 84 f5 05 00 00    	je     0x611
  1c:	83 3d f6 8e 09 18 00 	cmpl   $0x0,0x18098ef6(%rip)        # 0x18098f19
  23:	75 13                	jne    0x38
  25:	48 63 44 24 20       	movslq 0x20(%rsp),%rax
* 2a:	48 0f a3 05 87 ff 05 	bt     %rax,0x1205ff87(%rip)        # 0x1205ffb9 <-- trapping instruction
  31:	12
  32:	0f 83 15 05 00 00    	jae    0x54d
  38:	31 ed                	xor    %ebp,%ebp
  3a:	48 8b 3c 24          	mov    (%rsp),%rdi
  3e:	4c                   	rex.WR
  3f:	8b                   	.byte 0x8b

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/22 02:24 upstream 89be9a83ccf1 1555463b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs BUG: unable to handle kernel paging request in srcu_gp_start_if_needed
* Struck through repros no longer work on HEAD.