[syzbot] [block?] general protection fault in bio_alloc_bioset

[syzbot <syzbot+09ddb593eea76a158f42@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    8e42d2514a7e Add linux-next specific files for 20260318
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10b35ed6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1da705b17f2649a3
dashboard link: https://syzkaller.appspot.com/bug?extid=09ddb593eea76a158f42
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1325a06a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/64c940773401/disk-8e42d251.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aa7a94376665/vmlinux-8e42d251.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5a7ab603c859/bzImage-8e42d251.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09ddb593eea76a158f42@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 1116 Comm: kworker/u8:9 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: writeback wb_workfn (flush-8:0)
RIP: 0010:bio_init block/bio.c:214 [inline]
RIP: 0010:bio_init_inline include/linux/bio.h:435 [inline]
RIP: 0010:bio_alloc_bioset+0x664/0xc10 block/bio.c:593
Code: 04 24 00 00 00 00 41 8d 46 ff 0f b7 d8 bf 04 00 00 00 89 de e8 6d b0 3a fd 66 83 fb 04 0f 83 db 00 00 00 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 3e 27 a4 fd 49 c7 07 00 00 00 00 49
RSP: 0000:ffffc9000576efe8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802998bd00 RSI: 0000000000000000 RDI: 0000000000000004
RBP: dffffc0000000000 R08: ffffffff905435f7 R09: 1ffffffff20a86be
R10: dffffc0000000000 R11: fffffbfff20a86bf R12: 0000000000092800
R13: ffffffff9a8dc840 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124de1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f51b88511d0 CR3: 0000000072570000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 bio_alloc include/linux/bio.h:373 [inline]
 submit_bh_wbc+0x22d/0x650 fs/buffer.c:2816
 __block_write_full_folio+0x810/0xe10 fs/buffer.c:1930
 blkdev_writepages+0xef/0x1b0 block/fops.c:486
 do_writepages+0x32e/0x550 mm/page-writeback.c:2554
 __writeback_single_inode+0x133/0x11a0 fs/fs-writeback.c:1750
 writeback_sb_inodes+0x992/0x1a20 fs/fs-writeback.c:2042
 __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2118
 wb_writeback+0x46a/0xb70 fs/fs-writeback.c:2229
 wb_check_start_all fs/fs-writeback.c:2355 [inline]
 wb_do_writeback fs/fs-writeback.c:2381 [inline]
 wb_workfn+0x95b/0xf50 fs/fs-writeback.c:2414
 process_one_work+0x9ab/0x1780 kernel/workqueue.c:3288
 process_scheduled_works kernel/workqueue.c:3379 [inline]
 worker_thread+0xba8/0x11e0 kernel/workqueue.c:3465
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bio_init block/bio.c:214 [inline]
RIP: 0010:bio_init_inline include/linux/bio.h:435 [inline]
RIP: 0010:bio_alloc_bioset+0x664/0xc10 block/bio.c:593
Code: 04 24 00 00 00 00 41 8d 46 ff 0f b7 d8 bf 04 00 00 00 89 de e8 6d b0 3a fd 66 83 fb 04 0f 83 db 00 00 00 4c 89 f8 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 ff e8 3e 27 a4 fd 49 c7 07 00 00 00 00 49
RSP: 0000:ffffc9000576efe8 EFLAGS: 00010246

RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88802998bd00 RSI: 0000000000000000 RDI: 0000000000000004
RBP: dffffc0000000000 R08: ffffffff905435f7 R09: 1ffffffff20a86be
R10: dffffc0000000000 R11: fffffbfff20a86bf R12: 0000000000092800
R13: ffffffff9a8dc840 R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124de1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564154e50330 CR3: 000000005d868000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	04 24                	add    $0x24,%al
   2:	00 00                	add    %al,(%rax)
   4:	00 00                	add    %al,(%rax)
   6:	41 8d 46 ff          	lea    -0x1(%r14),%eax
   a:	0f b7 d8             	movzwl %ax,%ebx
   d:	bf 04 00 00 00       	mov    $0x4,%edi
  12:	89 de                	mov    %ebx,%esi
  14:	e8 6d b0 3a fd       	call   0xfd3ab086
  19:	66 83 fb 04          	cmp    $0x4,%bx
  1d:	0f 83 db 00 00 00    	jae    0xfe
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 ff             	mov    %r15,%rdi
  33:	e8 3e 27 a4 fd       	call   0xfda42776
  38:	49 c7 07 00 00 00 00 	movq   $0x0,(%r15)
  3f:	49                   	rex.WB


---
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