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Message-ID: <20230705-aufgearbeitet-kaffee-44ff4731a7dd@brauner>
Date: Wed, 5 Jul 2023 15:05:56 +0200
From: Christian Brauner <brauner@...nel.org>
To: syzbot <syzbot+a67fc5321ffb4b311c98@...kaller.appspotmail.com>,
Jeff Layton <jlayton@...nel.org>, amir73il@...il.com
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-unionfs@...r.kernel.org, miklos@...redi.hu,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [overlayfs?] general protection fault in d_path
On Wed, Jul 05, 2023 at 05:00:45AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: d528014517f2 Revert ".gitignore: ignore *.cover and *.mbx"
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14fad002a80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=1085b4238c9eb6ba
> dashboard link: https://syzkaller.appspot.com/bug?extid=a67fc5321ffb4b311c98
> compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/fef94e788067/disk-d5280145.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/576412ea518b/vmlinux-d5280145.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/685a0e4be06b/bzImage-d5280145.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+a67fc5321ffb4b311c98@...kaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc000000000a: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000050-0x0000000000000057]
> CPU: 1 PID: 10127 Comm: syz-executor.3 Not tainted 6.4.0-syzkaller-11478-gd528014517f2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> RIP: 0010:__lock_acquire+0x10d/0x7f70 kernel/locking/lockdep.c:5012
> Code: 85 75 18 00 00 83 3d 15 c8 2c 0d 00 48 89 9c 24 10 01 00 00 0f 84 f8 0f 00 00 83 3d 5c de b3 0b 00 74 34 48 89 d0 48 c1 e8 03 <42> 80 3c 00 00 74 1a 48 89 d7 e8 b4 51 79 00 48 8b 94 24 80 00 00
> RSP: 0018:ffffc900169be9e0 EFLAGS: 00010006
> RAX: 000000000000000a RBX: 1ffff92002d37d60 RCX: 0000000000000002
> RDX: 0000000000000050 RSI: 0000000000000000 RDI: 0000000000000050
> RBP: ffffc900169beca8 R08: dffffc0000000000 R09: 0000000000000001
> R10: dffffc0000000000 R11: fffffbfff1d2fe76 R12: 0000000000000000
> R13: 0000000000000001 R14: 0000000000000002 R15: ffff88802091d940
> FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fa22a3fe000 CR3: 000000004b5e1000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <TASK>
> lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761
> seqcount_lockdep_reader_access+0x139/0x220 include/linux/seqlock.h:102
> get_fs_root_rcu fs/d_path.c:244 [inline]
> d_path+0x2f0/0x6e0 fs/d_path.c:286
> audit_log_d_path+0xd3/0x310 kernel/audit.c:2139
> 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:1202
> security_inode_getattr+0xd3/0x120 security/security.c:2114
> vfs_getattr+0x25/0x70 fs/stat.c:167
> ovl_getattr+0x1b1/0xf70 fs/overlayfs/inode.c:174
> ima_check_last_writer security/integrity/ima/ima_main.c:171 [inline]
> ima_file_free+0x26e/0x4b0 security/integrity/ima/ima_main.c:203
Ugh, I think the root of this might all be the call back into
vfs_getattr() that happens on overlayfs:
__fput()
-> ima_file_free()
-> mutex_lock()
-> vfs_getattr_nosec()
-> i_op->getattr() == ovl_getattr()
-> vfs_getattr()
-> security_inode_getattr()
-> mutex_unlock()
So either overlayfs needs to call vfs_getattr_nosec() when the request
comes from vfs_getattr_nosec() or this needs to use
backing_file_real_path() to operate on the real underlying path.
Thoughts?
> __fput+0x36a/0x950 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+0x1709/0x17e0 kernel/signal.c:2877
> arch_do_signal_or_restart+0x91/0x670 arch/x86/kernel/signal.c:308
> 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:286 [inline]
> syscall_exit_to_user_mode+0x64/0x280 kernel/entry/common.c:297
> do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f7f3ca8c389
> Code: Unable to access opcode bytes at 0x7f7f3ca8c35f.
> RSP: 002b:00007f7f3d741168 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
> RAX: fffffffffffffffb RBX: 00007f7f3cbac050 RCX: 00007f7f3ca8c389
> RDX: 0000000000000000 RSI: 00000000200001c0 RDI: 0000000020000180
> RBP: 00007f7f3cad7493 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fff8432555f R14: 00007f7f3d741300 R15: 0000000000022000
> </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:__lock_acquire+0x10d/0x7f70 kernel/locking/lockdep.c:5012
> Code: 85 75 18 00 00 83 3d 15 c8 2c 0d 00 48 89 9c 24 10 01 00 00 0f 84 f8 0f 00 00 83 3d 5c de b3 0b 00 74 34 48 89 d0 48 c1 e8 03 <42> 80 3c 00 00 74 1a 48 89 d7 e8 b4 51 79 00 48 8b 94 24 80 00 00
> RSP: 0018:ffffc900169be9e0 EFLAGS: 00010006
> RAX: 000000000000000a RBX: 1ffff92002d37d60 RCX: 0000000000000002
> RDX: 0000000000000050 RSI: 0000000000000000 RDI: 0000000000000050
> RBP: ffffc900169beca8 R08: dffffc0000000000 R09: 0000000000000001
> R10: dffffc0000000000 R11: fffffbfff1d2fe76 R12: 0000000000000000
> R13: 0000000000000001 R14: 0000000000000002 R15: ffff88802091d940
> FS: 0000000000000000(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fa22a3fe000 CR3: 000000004b5e1000 CR4: 00000000003506e0
> 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 15 c8 2c 0d 00 cmpl $0x0,0xd2cc815(%rip) # 0xd2cc821
> 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 5c de b3 0b 00 cmpl $0x0,0xbb3de5c(%rip) # 0xbb3de7d
> 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 51 79 00 callq 0x7951ed
> 39: 48 rex.W
> 3a: 8b .byte 0x8b
> 3b: 94 xchg %eax,%esp
> 3c: 24 80 and $0x80,%al
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want to change bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup
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