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Message-ID: <873204f28bb74add80cc5969f68f6a2840e8d41b.camel@linux.ibm.com>
Subject: Re: [syzbot] [integrity] [overlayfs] general protection fault in
 d_path
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     syzbot <syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com>,
        amir73il@gmail.com, brauner@kernel.org, jlayton@kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-unionfs@vger.kernel.org, miklos@szeredi.hu,
        syzkaller-bugs@googlegroups.com
Date:   Thu, 14 Sep 2023 13:54:32 -0400
In-Reply-To: <0000000000004e08ee060539e0a2@google.com>
References: <0000000000004e08ee060539e0a2@google.com>
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On Wed, 2023-09-13 at 02:06 -0700, syzbot wrote:
> Hello,
> 
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> general protection fault in d_path

Is an IMA policy being loaded?  Please include the boot command line.


> general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f]
> CPU: 0 PID: 5465 Comm: syz-executor.0 Not tainted 6.6.0-rc1-syzkaller-00004-g965067e2f71e #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
> RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:275 [inline]
> RIP: 0010:get_fs_root_rcu fs/d_path.c:244 [inline]
> RIP: 0010:d_path+0x2f0/0x6e0 fs/d_path.c:286
> Code: 30 00 74 08 48 89 df e8 be 20 e1 ff 4c 8b 23 4d 8d 6c 24 48 49 81 c4 88 00 00 00 4c 89 eb 48 c1 eb 03 4c 89 ef e8 00 1e 00 00 <42> 0f b6 04 33 84 c0 0f 85 89 00 00 00 45 8b 7d 00 44 89 fe 83 e6
> RSP: 0018:ffffc90005056ec0 EFLAGS: 00010246
> RAX: be27ea831a7ad800 RBX: 0000000000000009 RCX: ffff88801c713b80
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90005056fd0 R08: ffffffff82068d08 R09: 1ffffffff1d34ccd
> R10: dffffc0000000000 R11: fffffbfff1d34cce R12: 0000000000000088
> R13: 0000000000000048 R14: dffffc0000000000 R15: ffff888076dcc000
> FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f4b67d70420 CR3: 0000000016f66000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  audit_log_d_path+0xd3/0x310 kernel/audit.c:2138
>  dump_common_audit_data security/lsm_audit.c:224 [inline]
>  common_lsm_audit+0x7cf/0x1a90 security/lsm_audit.c:458
>  smack_log+0x421/0x540 security/smack/smack_access.c:383
>  smk_tskacc+0x2ff/0x360 security/smack/smack_access.c:253
>  smack_inode_getattr+0x203/0x270 security/smack/smack_lsm.c:1271
>  security_inode_getattr+0xd3/0x120 security/security.c:2153
>  vfs_getattr+0x2a/0x3a0 fs/stat.c:206
>  ovl_getattr+0x1b1/0xf70 fs/overlayfs/inode.c:174
>  ima_check_last_writer security/integrity/ima/ima_main.c:171 [inline]
>  ima_file_free+0x2c3/0x560 security/integrity/ima/ima_main.c:203
>  __fput+0x36a/0x910 fs/file_table.c:378
>  task_work_run+0x24a/0x300 kernel/task_work.c:179
>  exit_task_work include/linux/task_work.h:38 [inline]
>  do_exit+0x68f/0x2290 kernel/exit.c:874
>  do_group_exit+0x206/0x2c0 kernel/exit.c:1024
>  get_signal+0x175d/0x1840 kernel/signal.c:2892
>  arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:309
>  exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
>  exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
>  __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
>  syscall_exit_to_user_mode+0x64/0x280 kernel/entry/common.c:296
>  do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f2a67a7cae9
> Code: Unable to access opcode bytes at 0x7f2a67a7cabf.
> RSP: 002b:00007f2a6875c178 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: 0000000000000001 RBX: 00007f2a67b9bf88 RCX: 00007f2a67a7cae9
> RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00007f2a67b9bf8c
> RBP: 00007f2a67b9bf80 R08: 00007fffba3690b0 R09: 00007f2a6875c6c0
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2a67b9bf8c
> R13: 000000000000000b R14: 00007fffba21b880 R15: 00007fffba21b968
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__seqprop_spinlock_sequence include/linux/seqlock.h:275 [inline]
> RIP: 0010:get_fs_root_rcu fs/d_path.c:244 [inline]
> RIP: 0010:d_path+0x2f0/0x6e0 fs/d_path.c:286
> Code: 30 00 74 08 48 89 df e8 be 20 e1 ff 4c 8b 23 4d 8d 6c 24 48 49 81 c4 88 00 00 00 4c 89 eb 48 c1 eb 03 4c 89 ef e8 00 1e 00 00 <42> 0f b6 04 33 84 c0 0f 85 89 00 00 00 45 8b 7d 00 44 89 fe 83 e6
> RSP: 0018:ffffc90005056ec0 EFLAGS: 00010246
> RAX: be27ea831a7ad800 RBX: 0000000000000009 RCX: ffff88801c713b80
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90005056fd0 R08: ffffffff82068d08 R09: 1ffffffff1d34ccd
> R10: dffffc0000000000 R11: fffffbfff1d34cce R12: 0000000000000088
> R13: 0000000000000048 R14: dffffc0000000000 R15: ffff888076dcc000
> FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f4b67d70420 CR3: 0000000016f66000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:	30 00                	xor    %al,(%rax)
>    2:	74 08                	je     0xc
>    4:	48 89 df             	mov    %rbx,%rdi
>    7:	e8 be 20 e1 ff       	call   0xffe120ca
>    c:	4c 8b 23             	mov    (%rbx),%r12
>    f:	4d 8d 6c 24 48       	lea    0x48(%r12),%r13
>   14:	49 81 c4 88 00 00 00 	add    $0x88,%r12
>   1b:	4c 89 eb             	mov    %r13,%rbx
>   1e:	48 c1 eb 03          	shr    $0x3,%rbx
>   22:	4c 89 ef             	mov    %r13,%rdi
>   25:	e8 00 1e 00 00       	call   0x1e2a
> * 2a:	42 0f b6 04 33       	movzbl (%rbx,%r14,1),%eax <-- trapping instruction
>   2f:	84 c0                	test   %al,%al
>   31:	0f 85 89 00 00 00    	jne    0xc0
>   37:	45 8b 7d 00          	mov    0x0(%r13),%r15d
>   3b:	44 89 fe             	mov    %r15d,%esi
>   3e:	83                   	.byte 0x83
>   3f:	e6                   	.byte 0xe6
> 
> 
> Tested on:
> 
> commit:         965067e2 ima: fix wrong dereferences of file->f_path
> git tree:       https://github.com/amir73il/linux ima-ovl-fix
> console output: https://syzkaller.appspot.com/x/log.txt?x=109b00e8680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
> dashboard link: https://syzkaller.appspot.com/bug?extid=a67fc5321ffb4b311c98
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> Note: no patches were applied.