Re: [syzbot] Re: [syzbot] [fs?] general protection fault in pagemap_scan_hugetlb_entry

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Subject: Re: [syzbot] [fs?] general protection fault in pagemap_scan_hugetlb_entry
Author: sidhartha.kumar@oracle.com

#syz test

________________________________
From: syzbot <syzbot+6e2ccedb96d1174e6a5f@syzkaller.appspotmail.com>
Sent: Saturday, December 2, 2023 6:17 PM
To: akpm@linux-foundation.org <akpm@linux-foundation.org>; dan.carpenter@linaro.org <dan.carpenter@linaro.org>; linux-fsdevel@vger.kernel.org <linux-fsdevel@vger.kernel.org>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; linux-mm@kvack.org <linux-mm@kvack.org>; llvm@lists.linux.dev <llvm@lists.linux.dev>; Mike Kravetz <mike.kravetz@oracle.com>; muchun.song@linux.dev <muchun.song@linux.dev>; nathan@kernel.org <nathan@kernel.org>; ndesaulniers@google.com <ndesaulniers@google.com>; Sidhartha Kumar <sidhartha.kumar@oracle.com>; syzkaller-bugs@googlegroups.com <syzkaller-bugs@googlegroups.com>; trix@redhat.com <trix@redhat.com>
Subject: [syzbot] [fs?] general protection fault in pagemap_scan_hugetlb_entry

Hello,

syzbot found the following issue on:

HEAD commit:    df60cee26a2e Merge tag '6.7-rc3-smb3-server-fixes' of git:..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=17ad46fce80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bb39fe85d254f638
dashboard link: https://syzkaller.appspot.com/bug?extid=6e2ccedb96d1174e6a5f
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17befd62e80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10d5a90ce80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c632017e0dc4/disk-df60cee2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f94c8fa25aeb/vmlinux-df60cee2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/af80f80c708b/bzImage-df60cee2.xz

The issue was bisected to:

commit a08c7193e4f18dc8508f2d07d0de2c5b94cb39a3
Author: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Date:   Tue Sep 26 19:20:17 2023 +0000

    mm/filemap: remove hugetlb special casing in filemap.c

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17f61552e80000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=140e1552e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=100e1552e80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6e2ccedb96d1174e6a5f@syzkaller.appspotmail.com
Fixes: a08c7193e4f1 ("mm/filemap: remove hugetlb special casing in filemap.c")

general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 5072 Comm: syz-executor107 Not tainted 6.7.0-rc3-syzkaller-00014-gdf60cee26a2e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
RIP: 0010:pagemap_scan_backout_range fs/proc/task_mmu.c:1946 [inline]
RIP: 0010:pagemap_scan_hugetlb_entry+0x6ca/0x1130 fs/proc/task_mmu.c:2254
Code: 3c 02 00 0f 85 68 09 00 00 48 8b 83 80 00 00 00 48 8d 04 40 4d 8d 6c c5 00 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 51 09 00 00 4d 8b 75 00 48 8b 7c 24 08 4c 89 f6
RSP: 0018:ffffc90003a2fa50 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffc90003a2fdb0 RCX: ffffffff82111e46
RDX: 0000000000000000 RSI: ffffffff82111e54 RDI: ffffc90003a2fe30
RBP: 1ffff92000745f52 R08: 0000000000000006 R09: 0000000020ffc000
R10: 00000000211f9000 R11: ffffffff915f5de8 R12: ffff8880299e0300
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000020ffc000
FS:  0000555555c7b380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005fdeb8 CR3: 00000000752b4000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 walk_hugetlb_range mm/pagewalk.c:326 [inline]
 __walk_page_range+0x36c/0x770 mm/pagewalk.c:393
 walk_page_range+0x626/0xa80 mm/pagewalk.c:521
 do_pagemap_scan+0x40d/0xcd0 fs/proc/task_mmu.c:2437
 do_pagemap_cmd+0x5e/0x80 fs/proc/task_mmu.c:2478
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl fs/ioctl.c:857 [inline]
 __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f171819d669
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffbe81bb68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fffbe81bb80 RCX: 00007f171819d669
RDX: 0000000020000040 RSI: 00000000c0606610 RDI: 0000000000000003
RBP: 00007f1718210610 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000286 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fffbe81bdb8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:pagemap_scan_backout_range fs/proc/task_mmu.c:1946 [inline]
RIP: 0010:pagemap_scan_hugetlb_entry+0x6ca/0x1130 fs/proc/task_mmu.c:2254
Code: 3c 02 00 0f 85 68 09 00 00 48 8b 83 80 00 00 00 48 8d 04 40 4d 8d 6c c5 00 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 51 09 00 00 4d 8b 75 00 48 8b 7c 24 08 4c 89 f6
RSP: 0018:ffffc90003a2fa50 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffffc90003a2fdb0 RCX: ffffffff82111e46
RDX: 0000000000000000 RSI: ffffffff82111e54 RDI: ffffc90003a2fe30
RBP: 1ffff92000745f52 R08: 0000000000000006 R09: 0000000020ffc000
R10: 00000000211f9000 R11: ffffffff915f5de8 R12: ffff8880299e0300
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000020ffc000
FS:  0000555555c7b380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005fdeb8 CR3: 00000000752b4000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:   3c 02                    cmp    $0x2,%al
   2:   00 0f                    add    %cl,(%rdi)
   4:   85 68 09                 test   %ebp,0x9(%rax)
   7:   00 00                    add    %al,(%rax)
   9:   48 8b 83 80 00 00 00     mov    0x80(%rbx),%rax
  10:   48 8d 04 40              lea    (%rax,%rax,2),%rax
  14:   4d 8d 6c c5 00           lea    0x0(%r13,%rax,8),%r13
  19:   48 b8 00 00 00 00 00     movabs $0xdffffc0000000000,%rax
  20:   fc ff df
  23:   4c 89 ea                 mov    %r13,%rdx
  26:   48 c1 ea 03              shr    $0x3,%rdx
* 2a:   80 3c 02 00              cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:   0f 85 51 09 00 00        jne    0x985
  34:   4d 8b 75 00              mov    0x0(%r13),%r14
  38:   48 8b 7c 24 08           mov    0x8(%rsp),%rdi
  3d:   4c 89 f6                 mov    %r14,%rsi


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