Re: [syzbot] [net?] kernel BUG in filemap_fault (2)

[syzbot <syzbot+263f159eb37a1c4c67a4@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    b4911fb0b060 Merge tag 'mmc-v6.16-rc1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16568c8c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3f6ddf055b5c86f8
dashboard link: https://syzkaller.appspot.com/bug?extid=263f159eb37a1c4c67a4
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=157cf48c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=146a948c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5828d857f454/disk-b4911fb0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ecf6b7e29d2b/vmlinux-b4911fb0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cc43b227e03d/bzImage-b4911fb0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+263f159eb37a1c4c67a4@syzkaller.appspotmail.com

 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_node_noprof+0x1bb/0x3c0 mm/slub.c:4249
 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:660
 alloc_skb include/linux/skbuff.h:1336 [inline]
 __ip6_append_data+0x2b8c/0x3de0 net/ipv6/ip6_output.c:1668
 ip6_append_data+0x1c4/0x380 net/ipv6/ip6_output.c:1858
 rawv6_sendmsg+0x124b/0x17f0 net/ipv6/raw.c:911
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x19c/0x270 net/socket.c:727
 ____sys_sendmsg+0x52d/0x830 net/socket.c:2566
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
 __sys_sendmmsg+0x227/0x430 net/socket.c:2709
------------[ cut here ]------------
kernel BUG at mm/filemap.c:3442!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 9236 Comm: syz.3.1035 Not tainted 6.16.0-rc4-syzkaller-00049-gb4911fb0b060 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:filemap_fault+0x117d/0x1200 mm/filemap.c:3442
Code: 38 c1 0f 8c 8e fc ff ff 4c 89 e7 e8 8d 6b 29 00 e9 81 fc ff ff e8 a3 13 c8 ff 48 89 df 48 c7 c6 a0 30 94 8b e8 d4 ae 0d 00 90 <0f> 0b e8 8c 13 c8 ff 48 8b 3c 24 48 c7 c6 20 37 94 8b e8 bc ae 0d
RSP: 0018:ffffc900030976e0 EFLAGS: 00010246
RAX: 864bab26a5780700 RBX: ffffea0001e53880 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8d96e815 RDI: 00000000ffffffff
RBP: ffffc90003097818 R08: ffffffff8f9fdbf7 R09: 1ffffffff1f3fb7e
R10: dffffc0000000000 R11: fffffbfff1f3fb7f R12: dffffc0000000000
R13: 1ffffd40003ca711 R14: ffffea0001e53898 R15: ffffea0001e53888
FS:  00007f9550ed76c0(0000) GS:ffff888125d84000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002000 CR3: 0000000059b4a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __do_fault+0x135/0x390 mm/memory.c:5169
 do_shared_fault mm/memory.c:5654 [inline]
 do_fault mm/memory.c:5728 [inline]
 do_pte_missing mm/memory.c:4251 [inline]
 handle_pte_fault mm/memory.c:6069 [inline]
 __handle_mm_fault+0x198b/0x5620 mm/memory.c:6212
 handle_mm_fault+0x2d5/0x7f0 mm/memory.c:6381
 do_user_addr_fault+0x764/0x1390 arch/x86/mm/fault.c:1387
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:__put_user_4+0xd/0x20 arch/x86/lib/putuser.S:94
Code: 66 89 01 31 c9 0f 01 ca e9 00 3b 03 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb <89> 01 31 c9 0f 01 ca e9 d7 3a 03 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90003097c98 EFLAGS: 00050206
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00002000000015b8
RDX: 0000000000000000 RSI: ffffffff8db5a681 RDI: ffffffff8be1b940
RBP: ffffc90003097eb0 R08: 0000000000000000 R09: ffffffff820a3bc0
R10: dffffc0000000000 R11: ffffed100b371081 R12: 0000200000001580
R13: 0000000000040000 R14: 0000200000000480 R15: 0000000000000044
 __sys_sendmmsg+0x25f/0x430 net/socket.c:2714
 __do_sys_sendmmsg net/socket.c:2736 [inline]
 __se_sys_sendmmsg net/socket.c:2733 [inline]
 __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2733
 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: 0033:0x7f954ff8e929
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:00007f9550ed7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f95501b5fa0 RCX: 00007f954ff8e929
RDX: 00000000000002e9 RSI: 0000200000000480 RDI: 0000000000000004
RBP: 00007f9550010b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f95501b5fa0 R15: 00007ffcd704c578
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:filemap_fault+0x117d/0x1200 mm/filemap.c:3442
Code: 38 c1 0f 8c 8e fc ff ff 4c 89 e7 e8 8d 6b 29 00 e9 81 fc ff ff e8 a3 13 c8 ff 48 89 df 48 c7 c6 a0 30 94 8b e8 d4 ae 0d 00 90 <0f> 0b e8 8c 13 c8 ff 48 8b 3c 24 48 c7 c6 20 37 94 8b e8 bc ae 0d
RSP: 0018:ffffc900030976e0 EFLAGS: 00010246
RAX: 864bab26a5780700 RBX: ffffea0001e53880 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8d96e815 RDI: 00000000ffffffff
RBP: ffffc90003097818 R08: ffffffff8f9fdbf7 R09: 1ffffffff1f3fb7e
R10: dffffc0000000000 R11: fffffbfff1f3fb7f R12: dffffc0000000000
R13: 1ffffd40003ca711 R14: ffffea0001e53898 R15: ffffea0001e53888
FS:  00007f9550ed76c0(0000) GS:ffff888125d84000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002000 CR3: 0000000059b4a000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	66 89 01             	mov    %ax,(%rcx)
   3:	31 c9                	xor    %ecx,%ecx
   5:	0f 01 ca             	clac
   8:	e9 00 3b 03 00       	jmp    0x33b0d
   d:	90                   	nop
   e:	90                   	nop
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	90                   	nop
  1c:	90                   	nop
  1d:	48 89 cb             	mov    %rcx,%rbx
  20:	48 c1 fb 3f          	sar    $0x3f,%rbx
  24:	48 09 d9             	or     %rbx,%rcx
  27:	0f 01 cb             	stac
* 2a:	89 01                	mov    %eax,(%rcx) <-- trapping instruction
  2c:	31 c9                	xor    %ecx,%ecx
  2e:	0f 01 ca             	clac
  31:	e9 d7 3a 03 00       	jmp    0x33b0d
  36:	90                   	nop
  37:	90                   	nop
  38:	90                   	nop
  39:	90                   	nop
  3a:	90                   	nop
  3b:	90                   	nop
  3c:	90                   	nop
  3d:	90                   	nop
  3e:	90                   	nop
  3f:	90                   	nop


---
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