linux-kernel - [syzbot] [mm?] general protection fault in ksm_do

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Message-ID: <0000000000006ef2e80620a73de3@google.com>
Date: Tue, 27 Aug 2024 02:55:22 -0700
From: syzbot <syzbot+ab2cf748d72119c9c291@...kaller.appspotmail.com>
To: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [mm?] general protection fault in ksm_do_scan

Hello,

syzbot found the following issue on:

HEAD commit:    3e9bff3bbe13 Merge tag 'vfs-6.11-rc6.fixes' of gitolite.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1112122b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8605cd35ddc8ff3c
dashboard link: https://syzkaller.appspot.com/bug?extid=ab2cf748d72119c9c291
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/93f88e5414fe/disk-3e9bff3b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0e9efe39c78f/vmlinux-3e9bff3b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9963bfff0cc9/bzImage-3e9bff3b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ab2cf748d72119c9c291@...kaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000084: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000420-0x0000000000000427]
CPU: 0 UID: 0 PID: 36 Comm: ksmd Not tainted 6.11.0-rc5-syzkaller-00015-g3e9bff3bbe13 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:scan_get_next_rmap_item mm/ksm.c:2557 [inline]
RIP: 0010:ksm_do_scan+0x792/0x6700 mm/ksm.c:2669
Code: 89 e7 48 c7 c6 ff ff ff ff e8 8a 72 b2 09 49 89 c6 48 85 c0 4c 89 7c 24 58 0f 84 c9 0a 00 00 49 8d 5e 20 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 ff 60 01 00 48 8b 1b be 00 00 00
RSP: 0018:ffffc90000ac7b60 EFLAGS: 00010217
RAX: 0000000000000084 RBX: 0000000000000426 RCX: ffff88801b6b8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000ac7d90 R08: ffffffff8babb624 R09: ffffffff8babb4a9
R10: 0000000000000004 R11: ffff88801b6b8000 R12: ffffc90000ac7ce0
R13: dffffc0000000000 R14: 0000000000000406 R15: ffff8880628826c4
FS:  0000000000000000(0000) GS:ffff8880b9200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556f065808 CR3: 000000006e7c6000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 ksm_scan_thread+0x110/0x490 mm/ksm.c:2694
 kthread+0x2f2/0x390 kernel/kthread.c:389
 ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:scan_get_next_rmap_item mm/ksm.c:2557 [inline]
RIP: 0010:ksm_do_scan+0x792/0x6700 mm/ksm.c:2669
Code: 89 e7 48 c7 c6 ff ff ff ff e8 8a 72 b2 09 49 89 c6 48 85 c0 4c 89 7c 24 58 0f 84 c9 0a 00 00 49 8d 5e 20 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 ff 60 01 00 48 8b 1b be 00 00 00
RSP: 0018:ffffc90000ac7b60 EFLAGS: 00010217
RAX: 0000000000000084 RBX: 0000000000000426 RCX: ffff88801b6b8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90000ac7d90 R08: ffffffff8babb624 R09: ffffffff8babb4a9
R10: 0000000000000004 R11: ffff88801b6b8000 R12: ffffc90000ac7ce0
R13: dffffc0000000000 R14: 0000000000000406 R15: ffff8880628826c4
FS:  0000000000000000(0000) GS:ffff8880b9300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdc1b0e7ab8 CR3: 0000000023394000 CR4: 0000000000350ef0
----------------
Code disassembly (best guess):
   0:	89 e7                	mov    %esp,%edi
   2:	48 c7 c6 ff ff ff ff 	mov    $0xffffffffffffffff,%rsi
   9:	e8 8a 72 b2 09       	call   0x9b27298
   e:	49 89 c6             	mov    %rax,%r14
  11:	48 85 c0             	test   %rax,%rax
  14:	4c 89 7c 24 58       	mov    %r15,0x58(%rsp)
  19:	0f 84 c9 0a 00 00    	je     0xae8
  1f:	49 8d 5e 20          	lea    0x20(%r14),%rbx
  23:	48 89 d8             	mov    %rbx,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	48 89 df             	mov    %rbx,%rdi
  34:	e8 ff 60 01 00       	call   0x16138
  39:	48 8b 1b             	mov    (%rbx),%rbx
  3c:	be                   	.byte 0xbe
  3d:	00 00                	add    %al,(%rax)


---
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