[syzbot] [fs?] [trace?] BUG: unable to handle kernel paging request in tracefs_apply_options

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 453f5db0619e Merge tag 'trace-v6.7-rc7' of git://git.kerne..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10ec3829e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=f8e72bae38c079e4
dashboard link: https://syzkaller.appspot.com/bug?extid=f8a023e0c6beabe2371a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1414af31e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15e52409e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/38b92a7149e8/disk-453f5db0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4f872267133f/vmlinux-453f5db0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/587572061791/bzImage-453f5db0.xz

The issue was bisected to:

commit 7e8358edf503e87236c8d07f69ef0ed846dd5112
Author: Steven Rostedt (Google) <ros...@goodmis.org>
Date: Fri Dec 22 00:07:57 2023 +0000

eventfs: Fix file and directory uid and gid ownership

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=108cd519e80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=128cd519e80000
console output: https://syzkaller.appspot.com/x/log.txt?x=148cd519e80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8a023...@syzkaller.appspotmail.com
Fixes: 7e8358edf503 ("eventfs: Fix file and directory uid and gid ownership")

BUG: unable to handle page fault for address: fffffffffffffff0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD d734067 P4D d734067 PUD d736067 PMD 0
Oops: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 5056 Comm: syz-executor170 Not tainted 6.7.0-rc7-syzkaller-00049-g453f5db0619e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
RIP: 0010:set_gid fs/tracefs/inode.c:224 [inline]
RIP: 0010:tracefs_apply_options+0x4d0/0xa40 fs/tracefs/inode.c:337
Code: 24 10 49 8b 1e 48 83 c3 f0 74 3d 48 89 d8 48 c1 e8 03 48 bd 00 00 00 00 00 fc ff df 80 3c 28 00 74 08 48 89 df e8 70 ff 88 fe <48> 8b 1b 48 89 de 48 83 e6 02 31 ff e8 bf fe 2c fe 48 83 e3 02 75
RSP: 0018:ffffc900040ffca8 EFLAGS: 00010246
RAX: 1ffffffffffffffe RBX: fffffffffffffff0 RCX: ffff888014bf5940
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffc900040ffc20
RBP: dffffc0000000000 R08: 0000000000000003 R09: fffff5200081ff84
R10: dffffc0000000000 R11: fffff5200081ff84 R12: ffff88801d743888
R13: ffff88801b0c3710 R14: ffff88801d7437e8 R15: ffff88801d743810
FS: 00005555557dd480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffff0 CR3: 000000001ec48000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
tracefs_remount+0x78/0x80 fs/tracefs/inode.c:353
reconfigure_super+0x440/0x870 fs/super.c:1143
do_remount fs/namespace.c:2884 [inline]
path_mount+0xc24/0xfa0 fs/namespace.c:3656
do_mount fs/namespace.c:3677 [inline]
__do_sys_mount fs/namespace.c:3886 [inline]
__se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3863
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x45/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7fec326e8d99
Code: 48 83 c4 28 c3 e8 67 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:00007ffc8103ddf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc8103de00 RCX: 00007fec326e8d99
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000000
RBP: 00007ffc8103de08 R08: 0000000020000140 R09: 00007fec326b5b80
R10: 0000000002200022 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc8103e068 R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
CR2: fffffffffffffff0
---[ end trace 0000000000000000 ]---
RIP: 0010:set_gid fs/tracefs/inode.c:224 [inline]
RIP: 0010:tracefs_apply_options+0x4d0/0xa40 fs/tracefs/inode.c:337
Code: 24 10 49 8b 1e 48 83 c3 f0 74 3d 48 89 d8 48 c1 e8 03 48 bd 00 00 00 00 00 fc ff df 80 3c 28 00 74 08 48 89 df e8 70 ff 88 fe <48> 8b 1b 48 89 de 48 83 e6 02 31 ff e8 bf fe 2c fe 48 83 e3 02 75
RSP: 0018:ffffc900040ffca8 EFLAGS: 00010246
RAX: 1ffffffffffffffe RBX: fffffffffffffff0 RCX: ffff888014bf5940
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffffc900040ffc20
RBP: dffffc0000000000 R08: 0000000000000003 R09: fffff5200081ff84
R10: dffffc0000000000 R11: fffff5200081ff84 R12: ffff88801d743888
R13: ffff88801b0c3710 R14: ffff88801d7437e8 R15: ffff88801d743810
FS: 00005555557dd480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffff0 CR3: 000000001ec48000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 24 10 and $0x10,%al
2: 49 8b 1e mov (%r14),%rbx
5: 48 83 c3 f0 add $0xfffffffffffffff0,%rbx
9: 74 3d je 0x48
b: 48 89 d8 mov %rbx,%rax
e: 48 c1 e8 03 shr $0x3,%rax
12: 48 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%rbp
19: fc ff df
1c: 80 3c 28 00 cmpb $0x0,(%rax,%rbp,1)
20: 74 08 je 0x2a
22: 48 89 df mov %rbx,%rdi
25: e8 70 ff 88 fe call 0xfe88ff9a
* 2a: 48 8b 1b mov (%rbx),%rbx <-- trapping instruction
2d: 48 89 de mov %rbx,%rsi
30: 48 83 e6 02 and $0x2,%rsi
34: 31 ff xor %edi,%edi
36: e8 bf fe 2c fe call 0xfe2cfefa
3b: 48 83 e3 02 and $0x2,%rbx
3f: 75 .byte 0x75


---
This report is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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#syz test: git://repo/address.git branch-or-commit-hash
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[Edward Adam Davis]

please test unable to handle kernel paging request in tracefs_apply_options

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 453f5db0619e

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 62524b20964e..51eacb5f4e08 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -220,9 +220,11 @@ static void set_gid(struct dentry *parent, kgid_t gid)
change_gid(dentry, gid);

/* If this is the events directory, update that too */
- ti = get_tracefs(dentry->d_inode);
- if (ti && (ti->flags & TRACEFS_EVENT_INODE))
- eventfs_update_gid(dentry, gid);
+ if (!IS_ERR_OR_NULL(dentry->d_inode)) {
+ ti = get_tracefs(dentry->d_inode);
+ if (ti && (ti->flags & TRACEFS_EVENT_INODE))
+ eventfs_update_gid(dentry, gid);
+ }

if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&this_parent->d_lock);

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+f8a023...@syzkaller.appspotmail.com

Tested on:

commit: 453f5db0 Merge tag 'trace-v6.7-rc7' of git://git.kerne..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=12992036e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=f8e72bae38c079e4
dashboard link: https://syzkaller.appspot.com/bug?extid=f8a023e0c6beabe2371a
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=10c2fef9e80000

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit ad579864637af46447208254719943179b69d41a

Author: Steven Rostedt (Google) <ros...@goodmis.org>

Date: Tue Jan 2 20:12:49 2024 +0000

tracefs: Check for dentry->d_inode exists in set_gid()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17659d24180000
start commit: 453f5db0619e Merge tag 'trace-v6.7-rc7' of git://git.kerne..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=f8e72bae38c079e4
dashboard link: https://syzkaller.appspot.com/bug?extid=f8a023e0c6beabe2371a

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1414af31e80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15e52409e80000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: tracefs: Check for dentry->d_inode exists in set_gid()

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.