Re: [syzbot] [mm?] general protection fault in __hugetlb_zap_begin

[syzbot <syzbot+ec9435c038e451be48ff@syzkaller.appspotmail.com>]

Hello,

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

general protection fault, probably for non-canonical address 0xdffffc000000001d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef]
CPU: 1 PID: 5726 Comm: syz-executor.3 Not tainted 6.6.0-rc6-next-20231018-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
RIP: 0010:__lock_acquire+0x10d/0x7f70 kernel/locking/lockdep.c:5004
Code: 85 75 18 00 00 83 3d fd 68 4d 0d 00 48 89 9c 24 10 01 00 00 0f 84 f8 0f 00 00 83 3d 0c 61 d2 0b 00 74 34 48 89 d0 48 c1 e8 03 <42> 80 3c 00 00 74 1a 48 89 d7 e8 b4 76 7d 00 48 8b 94 24 80 00 00
RSP: 0018:ffffc90005a37440 EFLAGS: 00010006
RAX: 000000000000001d RBX: 1ffff92000b46eac RCX: 0000000000000000
RDX: 00000000000000e8 RSI: 0000000000000000 RDI: 00000000000000e8
RBP: ffffc90005a37708 R08: dffffc0000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1d74f1e R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff888028368000
FS:  0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe062f6d48 CR3: 00000000282bd000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5753
 down_write+0x3a/0x50 kernel/locking/rwsem.c:1579
 __hugetlb_zap_begin+0x2e0/0x380 mm/hugetlb.c:5707
 hugetlb_zap_begin include/linux/hugetlb.h:258 [inline]
 unmap_vmas+0x364/0x5c0 mm/memory.c:1742
 exit_mmap+0x297/0xc50 mm/mmap.c:3308
 __mmput+0x115/0x3c0 kernel/fork.c:1349
 exit_mm+0x21f/0x300 kernel/exit.c:567
 do_exit+0x9b7/0x2750 kernel/exit.c:858
 __do_sys_exit kernel/exit.c:988 [inline]
 __se_sys_exit kernel/exit.c:986 [inline]
 __x64_sys_exit+0x40/0x40 kernel/exit.c:986
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x44/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f67fe27cae9
Code: Unable to access opcode bytes at 0x7f67fe27cabf.
RSP: 002b:00007f67fef73078 EFLAGS: 00000246
 ORIG_RAX: 000000000000003c
RAX: ffffffffffffffda RBX: 00007f67fe39bf80 RCX: 00007f67fe27cae9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f67fe2c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f67fe39bf80 R15: 00007ffdf414ed58
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__lock_acquire+0x10d/0x7f70 kernel/locking/lockdep.c:5004
Code: 85 75 18 00 00 83 3d fd 68 4d 0d 00 48 89 9c 24 10 01 00 00 0f 84 f8 0f 00 00 83 3d 0c 61 d2 0b 00 74 34 48 89 d0 48 c1 e8 03 <42> 80 3c 00 00 74 1a 48 89 d7 e8 b4 76 7d 00 48 8b 94 24 80 00 00
RSP: 0018:ffffc90005a37440 EFLAGS: 00010006

RAX: 000000000000001d RBX: 1ffff92000b46eac RCX: 0000000000000000
RDX: 00000000000000e8 RSI: 0000000000000000 RDI: 00000000000000e8
RBP: ffffc90005a37708 R08: dffffc0000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1d74f1e R12: 0000000000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff888028368000
FS:  0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe062f6d48 CR3: 00000000282bd000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	85 75 18             	test   %esi,0x18(%rbp)
   3:	00 00                	add    %al,(%rax)
   5:	83 3d fd 68 4d 0d 00 	cmpl   $0x0,0xd4d68fd(%rip)        # 0xd4d6909
   c:	48 89 9c 24 10 01 00 	mov    %rbx,0x110(%rsp)
  13:	00
  14:	0f 84 f8 0f 00 00    	je     0x1012
  1a:	83 3d 0c 61 d2 0b 00 	cmpl   $0x0,0xbd2610c(%rip)        # 0xbd2612d
  21:	74 34                	je     0x57
  23:	48 89 d0             	mov    %rdx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 00 00       	cmpb   $0x0,(%rax,%r8,1) <-- trapping instruction
  2f:	74 1a                	je     0x4b
  31:	48 89 d7             	mov    %rdx,%rdi
  34:	e8 b4 76 7d 00       	call   0x7d76ed
  39:	48                   	rex.W
  3a:	8b                   	.byte 0x8b
  3b:	94                   	xchg   %eax,%esp
  3c:	24 80                	and    $0x80,%al


Tested on:

commit:         2dac7569 Add linux-next specific files for 20231018
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=14bc60d7680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=29e8e23689e6210c
dashboard link: https://syzkaller.appspot.com/bug?extid=ec9435c038e451be48ff
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1088a55f680000