[syzbot] [bcachefs?] general protection fault in bch2_alloc_read

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 88264981f208 Merge tag 'sched_ext-for-6.12' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15a3de9f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e851828834875d6f
dashboard link: https://syzkaller.appspot.com/bug?extid=a1b59c8e1a3f022fd301
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=167ddca9980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13a3de9f980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-88264981.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/df2a0a047a7a/vmlinux-88264981.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bbdb25081712/bzImage-88264981.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2bfe5d0e1da4/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a1b59c...@syzkaller.appspotmail.com

bcachefs (loop0): accounting_read... done
bcachefs (loop0): alloc_read...
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 5100 Comm: syz-executor420 Not tainted 6.11.0-syzkaller-08481-g88264981f208 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:bch2_alloc_read+0x17d9/0x24f0 fs/bcachefs/alloc_background.c:625
Code: 0f b6 04 10 84 c0 4c 8d a4 24 b0 02 00 00 49 89 d7 0f 85 78 04 00 00 48 8b 33 48 8b 3c 24 e8 5e 14 00 00 48 89 c3 48 c1 e8 03 <42> 0f b6 04 38 84 c0 0f 85 74 04 00 00 0f b6 44 24 30 88 03 48 8b
RSP: 0018:ffffc90002d8f0e0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff89011e18963c
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 0000008100000014
RBP: ffffc90002d8f4c8 R08: ffffffff8409ef0e R09: 0000000000000000
R10: ffffc90002d8f450 R11: fffff520005b1e8c R12: ffffc90002d8f390
R13: 000000000000001c R14: ffffc90002d8f200 R15: dffffc0000000000
FS: 00005555882c4380(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000558280275240 CR3: 000000001205e000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
bch2_run_recovery_pass+0xf0/0x1e0 fs/bcachefs/recovery_passes.c:183
bch2_run_recovery_passes+0x19e/0x820 fs/bcachefs/recovery_passes.c:230
bch2_fs_recovery+0x24f9/0x38b0 fs/bcachefs/recovery.c:859
bch2_fs_start+0x356/0x5b0 fs/bcachefs/super.c:1036
bch2_fs_get_tree+0xd61/0x1700 fs/bcachefs/fs.c:1956
vfs_get_tree+0x90/0x2b0 fs/super.c:1800
do_new_mount+0x2be/0xb40 fs/namespace.c:3507
do_mount fs/namespace.c:3847 [inline]
__do_sys_mount fs/namespace.c:4055 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:4032
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: 0033:0x7f0c704b9dea
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:00007ffd5754dfb8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffd5754dfd0 RCX: 00007f0c704b9dea
RDX: 00000000200058c0 RSI: 0000000020005900 RDI: 00007ffd5754dfd0
RBP: 0000000000000004 R08: 00007ffd5754e010 R09: 002c61746f757172
R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000000
R13: 00007ffd5754e010 R14: 0000000000000003 R15: 0000000001000000
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_alloc_read+0x17d9/0x24f0 fs/bcachefs/alloc_background.c:625
Code: 0f b6 04 10 84 c0 4c 8d a4 24 b0 02 00 00 49 89 d7 0f 85 78 04 00 00 48 8b 33 48 8b 3c 24 e8 5e 14 00 00 48 89 c3 48 c1 e8 03 <42> 0f b6 04 38 84 c0 0f 85 74 04 00 00 0f b6 44 24 30 88 03 48 8b
RSP: 0018:ffffc90002d8f0e0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff89011e18963c
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 0000008100000014
RBP: ffffc90002d8f4c8 R08: ffffffff8409ef0e R09: 0000000000000000
R10: ffffc90002d8f450 R11: fffff520005b1e8c R12: ffffc90002d8f390
R13: 000000000000001c R14: ffffc90002d8f200 R15: dffffc0000000000
FS: 00005555882c4380(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4c02468cda CR3: 000000001205e000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 0f b6 04 10 movzbl (%rax,%rdx,1),%eax
4: 84 c0 test %al,%al
6: 4c 8d a4 24 b0 02 00 lea 0x2b0(%rsp),%r12
d: 00
e: 49 89 d7 mov %rdx,%r15
11: 0f 85 78 04 00 00 jne 0x48f
17: 48 8b 33 mov (%rbx),%rsi
1a: 48 8b 3c 24 mov (%rsp),%rdi
1e: e8 5e 14 00 00 call 0x1481
23: 48 89 c3 mov %rax,%rbx
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 0f b6 04 38 movzbl (%rax,%r15,1),%eax <-- trapping instruction
2f: 84 c0 test %al,%al
31: 0f 85 74 04 00 00 jne 0x4ab
37: 0f b6 44 24 30 movzbl 0x30(%rsp),%eax
3c: 88 03 mov %al,(%rbx)
3e: 48 rex.W
3f: 8b .byte 0x8b


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