linux-kernel - Re: [syzbot] [afs?] BUG: sleeping function called from invalid context in __alloc_frozen_pages

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Message-ID: <67e6e726.050a0220.2f068f.0080.GAE@google.com>
Date: Fri, 28 Mar 2025 11:15:02 -0700
From: syzbot <syzbot+3b6c5c6a1d0119b687a1@...kaller.appspotmail.com>
To: dhowells@...hat.com, linux-afs@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, marc.dionne@...istor.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [afs?] BUG: sleeping function called from invalid
 context in __alloc_frozen_pages_noprof

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in afs_dynroot_readdir

loop0: detected capacity change from 0 to 512
EXT4-fs: Ignoring removed bh option
EXT4-fs (loop0): mounting ext3 file system using the ext4 subsystem
EXT4-fs (loop0): 1 truncate cleaned up
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
============================================
WARNING: possible recursive locking detected
6.14.0-syzkaller-07422-gacb4f33713b9-dirty #0 Not tainted
--------------------------------------------
syz.0.16/6130 is trying to acquire lock:
ffff888011d70148 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: afs_dynroot_readdir+0x49e/0xb10 fs/afs/dynroot.c:351

but task is already holding lock:
ffff888011d70148 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: iterate_dir+0x4a6/0x760 fs/readdir.c:101

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&type->i_mutex_dir_key#9);
  lock(&type->i_mutex_dir_key#9);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.0.16/6130:
 #0: ffff88807e06bcf8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x310 fs/file.c:1213
 #1: ffff888011d70148 (&type->i_mutex_dir_key#9){.+.+}-{4:4}, at: iterate_dir+0x4a6/0x760 fs/readdir.c:101

stack backtrace:
CPU: 1 UID: 0 PID: 6130 Comm: syz.0.16 Not tainted 6.14.0-syzkaller-07422-gacb4f33713b9-dirty #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_deadlock_bug+0x2be/0x2d0 kernel/locking/lockdep.c:3042
 check_deadlock kernel/locking/lockdep.c:3094 [inline]
 validate_chain+0x928/0x24e0 kernel/locking/lockdep.c:3896
 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
 down_read+0xb3/0xa50 kernel/locking/rwsem.c:1524
 afs_dynroot_readdir+0x49e/0xb10 fs/afs/dynroot.c:351
 iterate_dir+0x5a9/0x760 fs/readdir.c:108
 __do_sys_getdents fs/readdir.c:322 [inline]
 __se_sys_getdents+0x1ff/0x4e0 fs/readdir.c:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdd5b98d169
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:00007fdd5c816038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007fdd5bba5fa0 RCX: 00007fdd5b98d169
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000004
RBP: 00007fdd5ba0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fdd5bba5fa0 R15: 00007ffe6a4f5bb8
 </TASK>


Tested on:

commit:         acb4f337 Merge tag 'm68knommu-for-v6.15' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10922a4c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=982413b40f90fdf8
dashboard link: https://syzkaller.appspot.com/bug?extid=3b6c5c6a1d0119b687a1
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17f51198580000