[syzbot] [bridge?] INFO: task hung in br_ioctl_stub (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 765e56e41a5a Merge tag 'v6.18rc7-SMB-client-fix' of git://..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159ace12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f
dashboard link: https://syzkaller.appspot.com/bug?extid=6bdeba54c73aa6a6219d
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12ddee12580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-765e56e4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fd649009c819/vmlinux-765e56e4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bf3e0d5c78c2/bzImage-765e56e4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6bdeba...@syzkaller.appspotmail.com

INFO: task syz.0.27:5720 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.27 state:D stack:28904 pid:5720 tgid:5719 ppid:5469 task_flags:0x400140 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
__mutex_lock_common kernel/locking/mutex.c:676 [inline]
__mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:760
br_ioctl_stub+0x199/0xc80 net/bridge/br_ioctl.c:418
br_ioctl_call net/socket.c:1227 [inline]
sock_ioctl+0x4d8/0x790 net/socket.c:1329
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f91bf78f7c9
RSP: 002b:00007f91c0675038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f91bf9e5fa0 RCX: 00007f91bf78f7c9
RDX: 0000200000000000 RSI: 00000000000089a2 RDI: 0000000000000003
RBP: 00007f91bf813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f91bf9e6038 R14: 00007f91bf9e5fa0 R15: 00007ffd440d2c68
</TASK>
INFO: task kworker/u4:11:5722 blocked for more than 150 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:11 state:D stack:28872 pid:5722 tgid:5722 ppid:2 task_flags:0x4208060 flags:0x00080000
Workqueue: events_unbound linkwatch_event
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
__mutex_lock_common kernel/locking/mutex.c:676 [inline]
__mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:760


---
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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[Arnav Kapoor]

#syz test: inode-timestamps-kcsan.patch
From f11640680f4c8b4f11b1c46b44a93ab81c69d751 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 1 Dec 2025 12:23:07 +0530
Subject: [PATCH] fs: use READ_ONCE/WRITE_ONCE for inode timestamp accessors to
 avoid benign KCSAN races

Reported-by: syzbot+c81800...@syzkaller.appspotmail.com
Signed-off-by: Arnav Kapoor <kapoor...@gmail.com>
---
 include/linux/fs.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index dd3b57cfa..53f9e8282 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1782,12 +1782,12 @@ struct timespec64 inode_set_ctime_deleg(struct inode *inode,
 
 static inline time64_t inode_get_atime_sec(const struct inode *inode)
 {
-       return inode->i_atime_sec;
+       return READ_ONCE(inode->i_atime_sec);
 }
 
 static inline long inode_get_atime_nsec(const struct inode *inode)
 {
-       return inode->i_atime_nsec;
+       return READ_ONCE(inode->i_atime_nsec);
 }
 
 static inline struct timespec64 inode_get_atime(const struct inode *inode)
@@ -1801,8 +1801,8 @@ static inline struct timespec64 inode_get_atime(const struct inode *inode)
 static inline struct timespec64 inode_set_atime_to_ts(struct inode *inode,
                                                      struct timespec64 ts)
 {
-       inode->i_atime_sec = ts.tv_sec;
-       inode->i_atime_nsec = ts.tv_nsec;
+       WRITE_ONCE(inode->i_atime_sec, ts.tv_sec);
+       WRITE_ONCE(inode->i_atime_nsec, ts.tv_nsec);
        return ts;
 }
 
@@ -1817,12 +1817,12 @@ static inline struct timespec64 inode_set_atime(struct inode *inode,
 
 static inline time64_t inode_get_mtime_sec(const struct inode *inode)
 {
-       return inode->i_mtime_sec;
+       return READ_ONCE(inode->i_mtime_sec);
 }
 
 static inline long inode_get_mtime_nsec(const struct inode *inode)
 {
-       return inode->i_mtime_nsec;
+       return READ_ONCE(inode->i_mtime_nsec);
 }
 
 static inline struct timespec64 inode_get_mtime(const struct inode *inode)
@@ -1835,8 +1835,8 @@ static inline struct timespec64 inode_get_mtime(const struct inode *inode)
 static inline struct timespec64 inode_set_mtime_to_ts(struct inode *inode,
                                                      struct timespec64 ts)
 {
-       inode->i_mtime_sec = ts.tv_sec;
-       inode->i_mtime_nsec = ts.tv_nsec;
+       WRITE_ONCE(inode->i_mtime_sec, ts.tv_sec);
+       WRITE_ONCE(inode->i_mtime_nsec, ts.tv_nsec);
        return ts;
 }
 
@@ -1861,12 +1861,12 @@ static inline struct timespec64 inode_set_mtime(struct inode *inode,
 
 static inline time64_t inode_get_ctime_sec(const struct inode *inode)
 {
-       return inode->i_ctime_sec;
+       return READ_ONCE(inode->i_ctime_sec);
 }
 
 static inline long inode_get_ctime_nsec(const struct inode *inode)
 {
-       return inode->i_ctime_nsec & ~I_CTIME_QUERIED;
+       return READ_ONCE(inode->i_ctime_nsec) & ~I_CTIME_QUERIED;
 }
 
 static inline struct timespec64 inode_get_ctime(const struct inode *inode)
--
2.43.0

[Aleksandr Nogikh]

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[syzbot]

> To view this discussion visit https://groups.google.com/d/msgid/syzkaller-bugs/CANp29Y6UJngxR20e5D86gyvJH7_HC2YKLCA8iX2HSWVZLX-YcQ%40mail.gmail.com.

I see the command but can't find the corresponding bug.
The email is sent to syzbo...@syzkaller.appspotmail.com address
but the HASH does not correspond to any known bug.
Please double check the address.