[syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    ce7f1a983b07 Add linux-next specific files for 20250923
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=118724e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
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=1376e27c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=136e78e2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c30be6f36c31/disk-ce7f1a98.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ae9ea347d4d8/vmlinux-ce7f1a98.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d59682a4f33c/bzImage-ce7f1a98.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com

BUG: sleeping function called from invalid context at fs/inode.c:1928
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6028, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
2 locks held by syz.0.17/6028:
 #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
 #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: hook_sb_delete+0xae/0xbd0 security/landlock/fs.c:1405
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 6028 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x495/0x610 kernel/sched/core.c:8960
 iput+0x2b/0xc50 fs/inode.c:1928
 hook_sb_delete+0x6b5/0xbd0 security/landlock/fs.c:1468
 security_sb_delete+0x80/0x150 security/security.c:1467
 generic_shutdown_super+0xaa/0x2c0 fs/super.c:634
 kill_anon_super fs/super.c:1281 [inline]
 kill_litter_super+0x76/0xb0 fs/super.c:1291
 deactivate_locked_super+0xbc/0x130 fs/super.c:473
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1327
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc08e18eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcd5efff18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fc08e3e5fa0 RCX: 00007fc08e18eec9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000002c0
RBP: 00007fc08e211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc08e3e5fa0 R14: 00007fc08e3e5fa0 R15: 0000000000000002
 </TASK>


---
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@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Hillf Danton]

> Date: Tue, 23 Sep 2025 15:59:37 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    ce7f1a983b07 Add linux-next specific files for 20250923
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=118724e2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
> dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
> 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=1376e27c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=136e78e2580000

#syz test

--- x/security/landlock/fs.c
+++ y/security/landlock/fs.c
@@ -1434,8 +1434,6 @@ static void hook_sb_delete(struct super_
 			spin_unlock(&inode->i_lock);
 			continue;
 		}
-		/* Keeps a reference to this inode until the next loop walk. */
-		__iget(inode);
 		spin_unlock(&inode->i_lock);
 
 		/*
@@ -1457,15 +1455,6 @@ static void hook_sb_delete(struct super_
 			 * It is therefore not necessary to lock inode->i_lock.
 			 */
 			rcu_assign_pointer(landlock_inode(inode)->object, NULL);
-			/*
-			 * At this point, we own the ihold() reference that was
-			 * originally set up by get_inode_object() and the
-			 * __iget() reference that we just set in this loop
-			 * walk.  Therefore the following call to iput() will
-			 * not sleep nor drop the inode because there is now at
-			 * least two references to it.
-			 */
-			iput(inode);
 		} else {
 			spin_unlock(&object->lock);
 			rcu_read_unlock();
@@ -1479,12 +1468,7 @@ static void hook_sb_delete(struct super_
 			 * disappear from under us until the next loop walk.
 			 */
 			spin_unlock(&sb->s_inode_list_lock);
-			/*
-			 * We can now actually put the inode reference from the
-			 * previous loop walk, which is not needed anymore.
-			 */
 			iput(prev_inode);
-			cond_resched();
 			spin_lock(&sb->s_inode_list_lock);
 		}
 		prev_inode = inode;
--

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

Hello,

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

Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
Tested-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com

Tested on:

commit:         ce7f1a98 Add linux-next specific files for 20250923
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13182142580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=108c8f12580000

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

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Edward Adam Davis]

#syz test

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 4ed997f4a663..a18d53507210 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1484,7 +1484,6 @@ static void hook_sb_delete(struct super_block *const sb)
 			 * previous loop walk, which is not needed anymore.
 			 */
 			iput(prev_inode);
-			cond_resched();
 			spin_lock(&sb->s_inode_list_lock);
 		}
 		prev_inode = inode;

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Edward Adam Davis]

#syz test

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 4ed997f4a663..a18d53507210 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -1484,7 +1484,6 @@ static void hook_sb_delete(struct super_block *const sb)
 			 * previous loop walk, which is not needed anymore.
 			 */
 			iput(prev_inode);
-			cond_resched();
 			spin_lock(&sb->s_inode_list_lock);
 		}
 		prev_inode = inode;
diff --git a/kernel/fork.c b/kernel/fork.c
index e9a7fb5c3e49..a0b8eeeb1d27 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2349,7 +2349,7 @@ __latent_entropy struct task_struct *copy_process(
 	if (need_futex_hash_allocate_default(clone_flags)) {
 		retval = futex_hash_allocate_default();
 		if (retval)
-			goto bad_fork_core_free;
+			goto bad_fork_cancel_cgroup;
 		/*
 		 * If we fail beyond this point we don't free the allocated
 		 * futex hash map. We assume that another thread will be created

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: sleeping function called from invalid context in hook_sb_delete

BUG: sleeping function called from invalid context at fs/inode.c:1928
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6514, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
2 locks held by syz.0.17/6514:
 #0: ffff8880306a20e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff8880306a20e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff8880306a20e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
 #1: ffff8880306a2998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #1: ffff8880306a2998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: hook_sb_delete+0xae/0xbc0 security/landlock/fs.c:1405
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 6514 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x495/0x610 kernel/sched/core.c:8960
 iput+0x2b/0xc50 fs/inode.c:1928
 hook_sb_delete+0x6b7/0xbc0 security/landlock/fs.c:1468
 security_sb_delete+0x80/0x150 security/security.c:1467
 generic_shutdown_super+0xaa/0x2c0 fs/super.c:634
 kill_anon_super fs/super.c:1281 [inline]
 kill_litter_super+0x76/0xb0 fs/super.c:1291
 deactivate_locked_super+0xbc/0x130 fs/super.c:473
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1327
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe6d878eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe6d961c038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007fe6d89e5fa0 RCX: 00007fe6d878eec9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000002c0
RBP: 00007fe6d8811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe6d89e6038 R14: 00007fe6d89e5fa0 R15: 00007ffc5011e858
 </TASK>


Tested on:

commit:         ce7f1a98 Add linux-next specific files for 20250923
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=128f94e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14e2cce2580000

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Edward Adam Davis]

#syz test: none

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

> #syz test: none

want either no args or 2 args (repo, branch), got 1

>

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Jan Kara]

Hello!

Added Landlock guys to CC since this is a bug in Landlock.

On Tue 23-09-25 15:59:37, syzbot wrote:
> syzbot found the following issue on:
> 
> HEAD commit:    ce7f1a983b07 Add linux-next specific files for 20250923
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=118724e2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
> dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
> 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=1376e27c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=136e78e2580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/c30be6f36c31/disk-ce7f1a98.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/ae9ea347d4d8/vmlinux-ce7f1a98.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/d59682a4f33c/bzImage-ce7f1a98.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
> 
> BUG: sleeping function called from invalid context at fs/inode.c:1928

The first catch from the new might_sleep() annotations in iput().

> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6028, name: syz.0.17
> preempt_count: 1, expected: 0
> RCU nest depth: 0, expected: 0
> 2 locks held by syz.0.17/6028:
>  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
>  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
>  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
>  #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
>  #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: hook_sb_delete+0xae/0xbd0 security/landlock/fs.c:1405
> Preemption disabled at:
> [<0000000000000000>] 0x0
> CPU: 0 UID: 0 PID: 6028 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>  __might_resched+0x495/0x610 kernel/sched/core.c:8960
>  iput+0x2b/0xc50 fs/inode.c:1928
>  hook_sb_delete+0x6b5/0xbd0 security/landlock/fs.c:1468

Indeed looks like a bug because we can call iput() while holding
sb->s_inode_list_lock in one case in hook_sb_delete().

								Honza

>  security_sb_delete+0x80/0x150 security/security.c:1467
>  generic_shutdown_super+0xaa/0x2c0 fs/super.c:634
>  kill_anon_super fs/super.c:1281 [inline]
>  kill_litter_super+0x76/0xb0 fs/super.c:1291
>  deactivate_locked_super+0xbc/0x130 fs/super.c:473
>  cleanup_mnt+0x425/0x4c0 fs/namespace.c:1327
>  task_work_run+0x1d4/0x260 kernel/task_work.c:227
>  resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
>  exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
>  exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
>  syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
>  syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
>  do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc08e18eec9
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffcd5efff18 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
> RAX: 0000000000000000 RBX: 00007fc08e3e5fa0 RCX: 00007fc08e18eec9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000002c0
> RBP: 00007fc08e211f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc08e3e5fa0 R14: 00007fc08e3e5fa0 R15: 0000000000000002
>  </TASK>
> 
> 
> ---
> 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@googlegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
> 
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: sleeping function called from invalid context in hook_sb_delete

BUG: sleeping function called from invalid context at fs/inode.c:1928
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6483, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
2 locks held by syz.0.17/6483:
 #0: ffff888028f400e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff888028f400e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff888028f400e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
 #1: ffff888028f40998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #1: ffff888028f40998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: hook_sb_delete+0xae/0xbc0 security/landlock/fs.c:1405
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 6483 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x495/0x610 kernel/sched/core.c:8960
 iput+0x2b/0xc50 fs/inode.c:1928
 hook_sb_delete+0x6b7/0xbc0 security/landlock/fs.c:1468
 security_sb_delete+0x80/0x150 security/security.c:1467
 generic_shutdown_super+0xaa/0x2c0 fs/super.c:634
 kill_anon_super fs/super.c:1281 [inline]
 kill_litter_super+0x76/0xb0 fs/super.c:1291
 deactivate_locked_super+0xbc/0x130 fs/super.c:473
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1327
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8b7e78eec9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8b7f714038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f8b7e9e5fa0 RCX: 00007f8b7e78eec9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00002000000002c0
RBP: 00007f8b7e811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8b7e9e6038 R14: 00007f8b7e9e5fa0 R15: 00007ffe75b4a848
 </TASK>


Tested on:

commit:         ce7f1a98 Add linux-next specific files for 20250923
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13644f12580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11724d34580000

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[Christian Brauner]

On Wed, Sep 24, 2025 at 01:05:03PM +0200, Jan Kara wrote:
> Hello!
> 
> Added Landlock guys to CC since this is a bug in Landlock.
> 
> On Tue 23-09-25 15:59:37, syzbot wrote:
> > syzbot found the following issue on:
> > 
> > HEAD commit:    ce7f1a983b07 Add linux-next specific files for 20250923
> > git tree:       linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=118724e2580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=1be6fa3d47bce66e
> > dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
> > 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=1376e27c580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=136e78e2580000
> > 
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/c30be6f36c31/disk-ce7f1a98.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/ae9ea347d4d8/vmlinux-ce7f1a98.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/d59682a4f33c/bzImage-ce7f1a98.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
> > 
> > BUG: sleeping function called from invalid context at fs/inode.c:1928
> 
> The first catch from the new might_sleep() annotations in iput().
> 
> > in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6028, name: syz.0.17
> > preempt_count: 1, expected: 0
> > RCU nest depth: 0, expected: 0
> > 2 locks held by syz.0.17/6028:
> >  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
> >  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
> >  #0: ffff8880326bc0e0 (&type->s_umount_key#48){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:505
> >  #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
> >  #1: ffff8880326bc998 (&s->s_inode_list_lock){+.+.}-{3:3}, at: hook_sb_delete+0xae/0xbd0 security/landlock/fs.c:1405
> > Preemption disabled at:
> > [<0000000000000000>] 0x0
> > CPU: 0 UID: 0 PID: 6028 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> > Call Trace:
> >  <TASK>
> >  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> >  __might_resched+0x495/0x610 kernel/sched/core.c:8960
> >  iput+0x2b/0xc50 fs/inode.c:1928
> >  hook_sb_delete+0x6b5/0xbd0 security/landlock/fs.c:1468
> 
> Indeed looks like a bug because we can call iput() while holding
> sb->s_inode_list_lock in one case in hook_sb_delete().

Very nice that the annotations help finding this!

Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

syzbot has bisected this issue to:

commit 2ef435a872abc347dc0a92f1c213bb0af3cbf195
Author: Max Kellermann <max.kellermann@ionos.com>
Date:   Wed Sep 17 15:36:31 2025 +0000

    fs: add might_sleep() annotation to iput() and more

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1092ba7c580000
start commit:   7c3ba4249a36 Add linux-next specific files for 20251008
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1292ba7c580000
console output: https://syzkaller.appspot.com/x/log.txt?x=1492ba7c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fa7a95b14b1eaa
dashboard link: https://syzkaller.appspot.com/bug?extid=12479ae15958fc3f54ec
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12280dcd980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=111d852f980000

Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
Fixes: 2ef435a872ab ("fs: add might_sleep() annotation to iput() and more")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Forwarded: Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: Re: [syzbot] [fs?] BUG: sleeping function called from invalid context in hook_sb_delete
Author: m@maowtm.org

#syz test

diff --git a/fs/inode.c b/fs/inode.c
index 1396f79b2551..b28a61978d88 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -812,6 +812,8 @@ static void evict(struct inode *inode)
 {
 	const struct super_operations *op = inode->i_sb->s_op;
 
+	might_sleep();
+
 	BUG_ON(!(inode_state_read_once(inode) & I_FREEING));
 	BUG_ON(!list_empty(&inode->i_lru));
 
@@ -1968,7 +1970,6 @@ static void iput_final(struct inode *inode)
  */
 void iput(struct inode *inode)
 {
-	might_sleep();
 	if (unlikely(!inode))
 		return;
 

Forwarded: [PATCH v1] fs: Move might_sleep() annotation to iput_final()

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH v1] fs: Move might_sleep() annotation to iput_final()
Author: mic@digikod.net

iput() don't directly call any sleepable code but mostly checks flags
and decrement a reference counter before calling iput_final() and then
evict().

Some code might call iput() with guarantees that iput_final() will not
be called.  This is the case for Landlock's hook_sb_delete() where the
inode counter must de decremented while holding it with another
reference, see comment above the first iput() call.

Move the new might_sleep() call from iput() to iput_final().  The
alternative would be to manually decrement the counter without calling
iput(), but it doesn't seem right.

Cc: Christian Brauner <brauner@kernel.org>
Cc: Edward Adam Davis <eadavis@qq.com>
Cc: Günther Noack <gnoack@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Max Kellermann <max.kellermann@ionos.com>
Cc: Tingmao Wang <m@maowtm.org>
Reported-by: syzbot+12479ae15958fc3f54ec@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68d32659.a70a0220.4f78.0012.GAE@google.com/
Fixes: 2ef435a872ab ("fs: add might_sleep() annotation to iput() and more")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
---

From hook_sb_delete():

	/*
	 * At this point, we own the ihold() reference that was
	 * originally set up by get_inode_object() and the
	 * __iget() reference that we just set in this loop
	 * walk.  Therefore the following call to iput() will
	 * not sleep nor drop the inode because there is now at
	 * least two references to it.
	 */
	iput(inode);

#syz test

---
 fs/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/inode.c b/fs/inode.c
index 84f539497857..64120cb21e8b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1917,6 +1917,7 @@ static void iput_final(struct inode *inode)
 	const struct super_operations *op = inode->i_sb->s_op;
 	int drop;
 
+	might_sleep();
 	WARN_ON(inode_state_read(inode) & I_NEW);
 	VFS_BUG_ON_INODE(atomic_read(&inode->i_count) != 0, inode);
 
@@ -1969,7 +1970,6 @@ static void iput_final(struct inode *inode)
  */
 void iput(struct inode *inode)
 {
-	might_sleep();
 	if (unlikely(!inode))
 		return;
 
-- 
2.51.0