Subject: [syzbot] linux-next test error: general protection fault in vma_merge

From: syzbot <[email-masked]>
Date: Sun, 26 Mar 2023 20:40:40 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    7c4a254d78f8 Add linux-next specific files for 20230323
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15f70246c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=20fd034702e6edd2
dashboard link: https://syzkaller.appspot.com/bug?extid=a2fd5af4a33891110a79
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dc0bbbecd2a5/disk-7c4a254d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6b2c8c7cfd4b/vmlinux-7c4a254d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ae312a388585/bzImage-7c4a254d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

general protection fault, probably for non-canonical address 0xdffffc0000000018: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000c0-0x00000000000000c7]
CPU: 1 PID: 5080 Comm: syz-fuzzer Not tainted 6.3.0-rc3-next-20230323-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:vma_merge+0x234/0x1fd0 mm/mmap.c:952
Code: 08 00 0f 84 b0 03 00 00 e8 e9 54 bf ff 48 8b 44 24 08 48 8d b8 a8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 18 00 00 48 8b 44 24 08 48 8b b0 a8 00 00 00
RSP: 0018:ffffc90003d0f998 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff88802974b800 RCX: 0000000000000000
RDX: 0000000000000018 RSI: ffffffff81c37957 RDI: 00000000000000c7
RBP: ffff888079aaa400 R08: 0000000000000006 R09: 0000000000000000
R10: 000000c001ffffff R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000000 R14: 000000c002000000 R15: 0000000000000000
FS:  000000c000524890(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe510676000 CR3: 00000000249a5000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 madvise_update_vma+0x23f/0xd40 mm/madvise.c:153
 madvise_vma_behavior+0x7f6/0x20e0 mm/madvise.c:1091
 madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1260
 do_madvise.part.0+0x193/0x470 mm/madvise.c:1439
 do_madvise mm/madvise.c:1452 [inline]
 __do_sys_madvise mm/madvise.c:1452 [inline]
 __se_sys_madvise mm/madvise.c:1450 [inline]
 __x64_sys_madvise+0x117/0x150 mm/madvise.c:1450
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x46b557
Code: 8b 24 24 48 8b 6c 24 10 48 83 c4 18 c3 cc cc cc cc cc cc 48 8b 7c 24 08 48 8b 74 24 10 8b 54 24 18 48 c7 c0 1c 00 00 00 0f 05 <89> 44 24 20 c3 cc cc cc cc 48 8b 7c 24 08 8b 74 24 10 8b 54 24 14
RSP: 002b:000000c00022de60 EFLAGS: 00000206 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 0000000000a12000 RCX: 000000000046b557
RDX: 000000000000000e RSI: 0000000000800000 RDI: 000000c001c00000
RBP: 000000c00022de88 R08: 0000000000000509 R09: 000000c001b6a000
R10: 00000000000012bd R11: 0000000000000206 R12: 0000000000000509
R13: 0000000000000003 R14: 000000c0003f1a00 R15: 00000000010e0700
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:vma_merge+0x234/0x1fd0 mm/mmap.c:952
Code: 08 00 0f 84 b0 03 00 00 e8 e9 54 bf ff 48 8b 44 24 08 48 8d b8 a8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 18 00 00 48 8b 44 24 08 48 8b b0 a8 00 00 00
RSP: 0018:ffffc90003d0f998 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff88802974b800 RCX: 0000000000000000
RDX: 0000000000000018 RSI: ffffffff81c37957 RDI: 00000000000000c7
RBP: ffff888079aaa400 R08: 0000000000000006 R09: 0000000000000000
R10: 000000c001ffffff R11: 0000000000000000 R12: 0000000000000001
R13: 0000000000000000 R14: 000000c002000000 R15: 0000000000000000
FS:  000000c000524890(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564702bbb078 CR3: 00000000249a5000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	08 00                	or     %al,(%rax)
   2:	0f 84 b0 03 00 00    	je     0x3b8
   8:	e8 e9 54 bf ff       	callq  0xffbf54f6
   d:	48 8b 44 24 08       	mov    0x8(%rsp),%rax
  12:	48 8d b8 a8 00 00 00 	lea    0xa8(%rax),%rdi
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 4d 18 00 00    	jne    0x1881
  34:	48 8b 44 24 08       	mov    0x8(%rsp),%rax
  39:	48 8b b0 a8 00 00 00 	mov    0xa8(%rax),%rsi

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