[syzbot] [mm?] general protection fault in sys_mremap

[syzbot <syzbot+e3385f43b2897a19be24@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    405e2241def8 Add linux-next specific files for 20250331
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=164c9bcf980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f2054704dd53fb80
dashboard link: https://syzkaller.appspot.com/bug?extid=e3385f43b2897a19be24
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7f800beaa14a/disk-405e2241.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a573ae9a8887/vmlinux-405e2241.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f4f732eedbc9/bzImage-405e2241.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e3385f43b2897a19be24@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
CPU: 0 UID: 0 PID: 6953 Comm: syz.1.290 Not tainted 6.14.0-next-20250331-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:vrm_uncharge mm/mremap.c:964 [inline]
RIP: 0010:expand_vma_in_place mm/mremap.c:1566 [inline]
RIP: 0010:expand_vma mm/mremap.c:1621 [inline]
RIP: 0010:mremap_at mm/mremap.c:1682 [inline]
RIP: 0010:do_mremap mm/mremap.c:1727 [inline]
RIP: 0010:__do_sys_mremap mm/mremap.c:1784 [inline]
RIP: 0010:__se_sys_mremap+0x25fa/0x2c00 mm/mremap.c:1752
Code: c0 0f 85 0e 05 00 00 0f b6 9c 24 20 03 00 00 31 ff 89 de e8 c8 16 ab ff 85 db 0f 84 7b 01 00 00 e8 bb 13 ab ff e9 9e 00 00 00 <80> 78 04 00 74 0a bf 20 00 00 00 e8 c6 2d 15 00 4c 8b 34 25 20 00
RSP: 0018:ffffc9001c347b40 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff92003868fca
RDX: ffffc9000d093000 RSI: 00000000000000e0 RDI: 00000000000000e1
RBP: ffffc9001c347f00 R08: ffffffff821d1414 R09: ffffffff8c2734a7
R10: 0000000000000004 R11: ffff888026f55a00 R12: 0000200000ff8000
R13: ffff888034282000 R14: 0000000018000098 R15: ffffc9001c347cd0
FS:  00007f975bfad6c0(0000) GS:ffff888124f95000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f975bf8bf98 CR3: 000000005c0a6000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f975b18d169
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:00007f975bfad038 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f975b3a6080 RCX: 00007f975b18d169
RDX: 0000000000002000 RSI: 0000000000001000 RDI: 0000200000ff8000
RBP: 00007f975b20e2a0 R08: 0000200000ff8000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f975b3a6080 R15: 00007ffe4ecc7008
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vrm_uncharge mm/mremap.c:964 [inline]
RIP: 0010:expand_vma_in_place mm/mremap.c:1566 [inline]
RIP: 0010:expand_vma mm/mremap.c:1621 [inline]
RIP: 0010:mremap_at mm/mremap.c:1682 [inline]
RIP: 0010:do_mremap mm/mremap.c:1727 [inline]
RIP: 0010:__do_sys_mremap mm/mremap.c:1784 [inline]
RIP: 0010:__se_sys_mremap+0x25fa/0x2c00 mm/mremap.c:1752
Code: c0 0f 85 0e 05 00 00 0f b6 9c 24 20 03 00 00 31 ff 89 de e8 c8 16 ab ff 85 db 0f 84 7b 01 00 00 e8 bb 13 ab ff e9 9e 00 00 00 <80> 78 04 00 74 0a bf 20 00 00 00 e8 c6 2d 15 00 4c 8b 34 25 20 00
RSP: 0018:ffffc9001c347b40 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff92003868fca
RDX: ffffc9000d093000 RSI: 00000000000000e0 RDI: 00000000000000e1
RBP: ffffc9001c347f00 R08: ffffffff821d1414 R09: ffffffff8c2734a7
R10: 0000000000000004 R11: ffff888026f55a00 R12: 0000200000ff8000
R13: ffff888034282000 R14: 0000000018000098 R15: ffffc9001c347cd0
FS:  00007f975bfad6c0(0000) GS:ffff888124f95000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f74d4f78ab8 CR3: 000000005c0a6000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	0f 85 0e 05 00 00    	jne    0x514
   6:	0f b6 9c 24 20 03 00 	movzbl 0x320(%rsp),%ebx
   d:	00
   e:	31 ff                	xor    %edi,%edi
  10:	89 de                	mov    %ebx,%esi
  12:	e8 c8 16 ab ff       	call   0xffab16df
  17:	85 db                	test   %ebx,%ebx
  19:	0f 84 7b 01 00 00    	je     0x19a
  1f:	e8 bb 13 ab ff       	call   0xffab13df
  24:	e9 9e 00 00 00       	jmp    0xc7
* 29:	80 78 04 00          	cmpb   $0x0,0x4(%rax) <-- trapping instruction
  2d:	74 0a                	je     0x39
  2f:	bf 20 00 00 00       	mov    $0x20,%edi
  34:	e8 c6 2d 15 00       	call   0x152dff
  39:	4c                   	rex.WR
  3a:	8b                   	.byte 0x8b
  3b:	34 25                	xor    $0x25,%al
  3d:	20 00                	and    %al,(%rax)


---
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