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Message-ID: <6960c392.050a0220.1c677c.03bf.GAE@google.com>
Date: Fri, 09 Jan 2026 01:00:02 -0800
From: syzbot <syzbot+b4a2af3000eaa84d95d5@...kaller.appspotmail.com>
To: kartikey406@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [btrfs?] general protection fault in create_empty_buffers
 (5)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in create_empty_buffers

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 6871 Comm: syz.0.175 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:create_empty_buffers+0x4d/0x480 fs/buffer.c:1694
Code: ea 6d ff 48 89 de ba 40 8c 40 00 4c 89 ef e8 0a f6 ff ff 49 89 c6 48 89 c3 eb 03 48 89 c3 e8 1a ea 6d ff 48 89 d8 48 c1 e8 03 <80> 3c 28 00 0f 85 81 03 00 00 48 8d 7b 08 4c 09 23 48 89 f8 48 c1
RSP: 0018:ffffc90003967870 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8250f9bc
RDX: ffff888025ef8000 RSI: ffffffff8250fe96 RDI: ffff888025ef9680
RBP: dffffc0000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: ffff888025ef8b30 R12: 0000000000000000
R13: ffffea0000a94200 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fe24bca76c0(0000) GS:ffff8880d68f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe24bca6f98 CR3: 0000000035a6c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 folio_create_buffers+0x109/0x150 fs/buffer.c:1802
 block_read_full_folio+0x14c/0x850 fs/buffer.c:2403
 filemap_read_folio+0xc8/0x2a0 mm/filemap.c:2496
 do_read_cache_folio+0x266/0x5c0 mm/filemap.c:4096
 do_read_cache_page mm/filemap.c:4162 [inline]
 read_cache_page_gfp+0x29/0x120 mm/filemap.c:4195
 btrfs_read_disk_super+0x201/0x580 fs/btrfs/volumes.c:1371
 btrfs_scan_one_device+0x109/0x820 fs/btrfs/volumes.c:1479
 btrfs_get_tree_super fs/btrfs/super.c:1860 [inline]
 btrfs_get_tree_subvol fs/btrfs/super.c:2089 [inline]
 btrfs_get_tree+0x5b3/0x2710 fs/btrfs/super.c:2123
 vfs_get_tree+0x8e/0x330 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount fs/namespace.c:3712 [inline]
 path_mount+0x7bf/0x23a0 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount fs/namespace.c:4201 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:4201
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe24ad8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007fe24bca7038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe24afe6090 RCX: 00007fe24ad8f7c9
RDX: 00002000000000c0 RSI: 0000200000000080 RDI: 00002000000001c0
RBP: 00007fe24ae13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004418 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe24afe6128 R14: 00007fe24afe6090 R15: 00007ffe2f937158
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:create_empty_buffers+0x4d/0x480 fs/buffer.c:1694
Code: ea 6d ff 48 89 de ba 40 8c 40 00 4c 89 ef e8 0a f6 ff ff 49 89 c6 48 89 c3 eb 03 48 89 c3 e8 1a ea 6d ff 48 89 d8 48 c1 e8 03 <80> 3c 28 00 0f 85 81 03 00 00 48 8d 7b 08 4c 09 23 48 89 f8 48 c1
RSP: 0018:ffffc90003967870 EFLAGS: 00010246

RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8250f9bc
RDX: ffff888025ef8000 RSI: ffffffff8250fe96 RDI: ffff888025ef9680
RBP: dffffc0000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: ffff888025ef8b30 R12: 0000000000000000
R13: ffffea0000a94200 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fe24bca76c0(0000) GS:ffff8880d68f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe24bca6f98 CR3: 0000000035a6c000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	6d                   	insl   (%dx),%es:(%rdi)
   1:	ff 48 89             	decl   -0x77(%rax)
   4:	de ba 40 8c 40 00    	fidivrs 0x408c40(%rdx)
   a:	4c 89 ef             	mov    %r13,%rdi
   d:	e8 0a f6 ff ff       	call   0xfffff61c
  12:	49 89 c6             	mov    %rax,%r14
  15:	48 89 c3             	mov    %rax,%rbx
  18:	eb 03                	jmp    0x1d
  1a:	48 89 c3             	mov    %rax,%rbx
  1d:	e8 1a ea 6d ff       	call   0xff6dea3c
  22:	48 89 d8             	mov    %rbx,%rax
  25:	48 c1 e8 03          	shr    $0x3,%rax
* 29:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2d:	0f 85 81 03 00 00    	jne    0x3b4
  33:	48 8d 7b 08          	lea    0x8(%rbx),%rdi
  37:	4c 09 23             	or     %r12,(%rbx)
  3a:	48 89 f8             	mov    %rdi,%rax
  3d:	48                   	rex.W
  3e:	c1                   	.byte 0xc1


Tested on:

commit:         623fb991 Merge tag 'pinctrl-v6.19-2' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=137de922580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
dashboard link: https://syzkaller.appspot.com/bug?extid=b4a2af3000eaa84d95d5
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1778a19a580000


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