From: Stefan Berger <stefanb@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-integrity@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-unionfs@vger.kernel.org,
miklos@szeredi.hu, syzkaller-bugs@googlegroups.com,
zohar@linux.ibm.com
Subject: Re: [syzbot] [integrity] [overlayfs] general protection fault in d_path
Date: Wed, 20 Sep 2023 13:01:24 -0400 [thread overview]
Message-ID: <bed99e92-cb7c-868d-94f3-ddf53e2b262a@linux.ibm.com> (raw)
In-Reply-To: <000000000000259bd8060596e33f@google.com>
On 9/17/23 20:04, syzbot wrote:
> syzbot has bisected this issue to:
>
> commit db1d1e8b9867aae5c3e61ad7859abfcc4a6fd6c7
> Author: Jeff Layton <jlayton@kernel.org>
> Date: Mon Apr 17 16:55:51 2023 +0000
>
> IMA: use vfs_getattr_nosec to get the i_version
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=106f7e54680000
> start commit: a747acc0b752 Merge tag 'linux-kselftest-next-6.6-rc2' of g..
> git tree: upstream
> final oops: https://syzkaller.appspot.com/x/report.txt?x=126f7e54680000
> console output: https://syzkaller.appspot.com/x/log.txt?x=146f7e54680000
> kernel config: https://syzkaller.appspot.com/x/.config?x=df91a3034fe3f122
> dashboard link: https://syzkaller.appspot.com/bug?extid=a67fc5321ffb4b311c98
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1671b694680000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ec94d8680000
>
> Reported-by: syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com
> Fixes: db1d1e8b9867 ("IMA: use vfs_getattr_nosec to get the i_version")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
The final oops shows this here:
BUG: kernel NULL pointer dereference, address: 0000000000000058
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 3192 Comm: syz-executor.0 Not tainted 6.4.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 08/04/2023
RIP: 0010:__lock_acquire+0x35/0x490 kernel/locking/lockdep.c:4946
Code: 83 ec 18 65 4c 8b 35 aa 60 f4 7e 83 3d b7 11 e4 02 00 0f 84 05 02
00 00 4c 89 cb 89 cd 41 89 d5 49 89 ff 83 fe 01 77 0c 89 f0 <49> 8b 44
c7 08 48 85 c0 75 1b 4c 89 ff 31 d2 45 89 c4 e8 74 f6 ff
RSP: 0018:ffffc90002edb840 EFLAGS: 00010097
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000050
RBP: 0000000000000002 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888102ea5340 R15: 0000000000000050
FS: 0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000058 CR3: 0000000003aa8000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lock_acquire+0xd8/0x1f0 kernel/locking/lockdep.c:5691
seqcount_lockdep_reader_access include/linux/seqlock.h:102 [inline]
get_fs_root_rcu fs/d_path.c:243 [inline]
d_path+0xd1/0x1f0 fs/d_path.c:285
audit_log_d_path+0x65/0x130 kernel/audit.c:2139
dump_common_audit_data security/lsm_audit.c:224 [inline]
common_lsm_audit+0x3b3/0x840 security/lsm_audit.c:458
smack_log+0xad/0x130 security/smack/smack_access.c:383
smk_tskacc+0xb1/0xd0 security/smack/smack_access.c:253
smack_inode_getattr+0x8a/0xb0 security/smack/smack_lsm.c:1187
security_inode_getattr+0x32/0x50 security/security.c:2114
vfs_getattr+0x1b/0x40 fs/stat.c:167
ovl_getattr+0xa6/0x3e0 fs/overlayfs/inode.c:173
ima_check_last_writer security/integrity/ima/ima_main.c:171 [inline]
ima_file_free+0xbd/0x130 security/integrity/ima/ima_main.c:203
__fput+0xc7/0x220 fs/file_table.c:315
task_work_run+0x7d/0xa0 kernel/task_work.c:179
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x2c7/0xa80 kernel/exit.c:871 <-----------------------
do_group_exit+0x85/0xa0 kernel/exit.c:1021
get_signal+0x73c/0x7f0 kernel/signal.c:2874
arch_do_signal_or_restart+0x89/0x290 arch/x86/kernel/signal.c:306
exit_to_user_mode_loop+0x61/0xb0 kernel/entry/common.c:168
exit_to_user_mode_prepare+0x64/0xb0 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x2b/0x1d0 kernel/entry/common.c:297
do_syscall_64+0x4d/0x90 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
do_exit has called exit_fs(tsk) [
https://elixir.bootlin.com/linux/v6.4-rc2/source/kernel/exit.c#L867 ]
exit_fs(tsk) has set tsk->fs = NULL [
https://elixir.bootlin.com/linux/v6.4-rc2/source/fs/fs_struct.c#L103 ]
I think this then bites in d_path() where it calls:
get_fs_root_rcu(current->fs, &root); [
https://elixir.bootlin.com/linux/v6.4-rc2/source/fs/d_path.c#L285 ]
current->fs is likely NULL here.
If this was correct it would have nothing to do with the actual patch,
though, but rather with the fact that smack logs on process termination.
I am not sure what the solution would be other than testing for
current->fs == NULL in d_path before using it and returning an error
that is not normally returned or trying to intercept this case in smack.
Stefan
next prev parent reply other threads:[~2023-09-20 17:06 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-05 12:00 [syzbot] [overlayfs?] general protection fault in d_path syzbot
2023-07-05 13:05 ` Christian Brauner
2023-07-05 13:39 ` Amir Goldstein
2023-07-05 13:41 ` Jeff Layton
2023-07-05 13:54 ` Amir Goldstein
2023-07-05 14:10 ` Jeff Layton
2023-09-12 22:10 ` syzbot
2023-09-13 7:09 ` Amir Goldstein
2023-09-13 9:06 ` [syzbot] [integrity] [overlayfs] " syzbot
2023-09-14 17:54 ` Mimi Zohar
2023-09-18 0:04 ` syzbot
2023-09-20 17:01 ` Stefan Berger [this message]
2023-09-20 20:37 ` Stefan Berger
2023-09-20 21:16 ` Jeff Layton
2023-09-20 22:09 ` Stefan Berger
2023-09-21 0:10 ` Stefan Berger
2023-09-21 0:52 ` Casey Schaufler
2023-09-21 10:32 ` Jeff Layton
2023-09-21 11:24 ` Mimi Zohar
2023-09-21 11:48 ` Christian Brauner
2023-09-21 14:29 ` Stefan Berger
2023-09-21 14:52 ` Mimi Zohar
2023-09-21 15:10 ` Jeff Layton
2023-09-21 15:18 ` Amir Goldstein
2023-09-21 15:19 ` Mimi Zohar
2023-09-21 15:39 ` Jeff Layton
2023-09-21 16:06 ` Mimi Zohar
2023-09-21 17:01 ` Amir Goldstein
2023-09-26 14:40 ` Mimi Zohar
2023-09-29 4:30 ` Amir Goldstein
2023-09-28 22:03 ` Stefan Berger
2023-09-29 4:25 ` Amir Goldstein
2023-09-29 12:39 ` Stefan Berger
2023-10-01 14:51 ` Amir Goldstein
2023-09-21 12:03 ` Amir Goldstein
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bed99e92-cb7c-868d-94f3-ddf53e2b262a@linux.ibm.com \
--to=stefanb@linux.ibm.com \
--cc=amir73il@gmail.com \
--cc=brauner@kernel.org \
--cc=jlayton@kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-integrity@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=syzbot+a67fc5321ffb4b311c98@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=zohar@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).