reply: [syzbot] [block?] BUG: corrupted list in loop_process_work

["黄朝阳 (Zhaoyang Huang)" <zhaoyang.huang@unisoc.com>]

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#syz test


Hello,

syzbot found the following issue on:

HEAD commit:    c674aa7c289e Add linux-next specific files for 20250212
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=125063f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a0fd539126ae5541
dashboard link: https://syzkaller.appspot.com/bug?extid=c104904eeb2c0edbdb06
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=158a3bdf980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17e18aa4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cc5b357d26d3/disk-c674aa7c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11dcf272a27b/vmlinux-c674aa7c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4e487b1c1c6e/bzImage-c674aa7c.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/4ea41e9eae4d/mount_0.gz

The issue was bisected to:

commit 3bee991f2b68175c828dc3f9c26367fe1827319a
Author: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Date:   Fri Feb 7 09:19:42 2025 +0000

    loop: release the lo_work_lock before queue_work

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=161029b0580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=151029b0580000
console output: https://syzkaller.appspot.com/x/log.txt?x=111029b0580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c104904eeb2c0edbdb06@syzkaller.appspotmail.com
Fixes: 3bee991f2b68 ("loop: release the lo_work_lock before queue_work")

list_add double add: new=ffff88807fe21c70, prev=ffff88807fe21c70, next=ffff888024c29160.
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:37!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:1 Not tainted 6.14.0-rc2-next-20250212-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: loop0 loop_workfn
RIP: 0010:__list_add_valid_or_report+0xa4/0x130 lib/list_debug.c:35
Code: f7 74 11 b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 48 c7 c7 40 e5 60 8c 4c 89 fe 4c 89 e2 4c 89 f1 e8 fd 88 35 fc 90 <0f> 0b 48 c7 c7 40 e3 60 8c e8 ee 88 35 fc 90 0f 0b 48 c7 c7 e0 e3
RSP: 0018:ffffc90000117628 EFLAGS: 00010046
RAX: 0000000000000058 RBX: 1ffff1100ffc438e RCX: 89e05f8d6ffcb000
RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
RBP: 1ffff1100498522d R08: ffffffff819f562c R09: 1ffff92000022e60
R10: dffffc0000000000 R11: fffff52000022e61 R12: ffff88807fe21c70
R13: dffffc0000000000 R14: ffff888024c29160 R15: ffff88807fe21c70
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4b64ffe00 CR3: 000000007cfa4000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __list_add_valid include/linux/list.h:88 [inline]
 __list_add include/linux/list.h:150 [inline]
 list_add_tail include/linux/list.h:183 [inline]
 loop_process_work+0x1f96/0x21c0 drivers/block/loop.c:1977
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
 worker_thread+0x870/0xd30 kernel/workqueue.c:3398
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__list_add_valid_or_report+0xa4/0x130 lib/list_debug.c:35
Code: f7 74 11 b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 48 c7 c7 40 e5 60 8c 4c 89 fe 4c 89 e2 4c 89 f1 e8 fd 88 35 fc 90 <0f> 0b 48 c7 c7 40 e3 60 8c e8 ee 88 35 fc 90 0f 0b 48 c7 c7 e0 e3
RSP: 0018:ffffc90000117628 EFLAGS: 00010046
RAX: 0000000000000058 RBX: 1ffff1100ffc438e RCX: 89e05f8d6ffcb000
RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
RBP: 1ffff1100498522d R08: ffffffff819f562c R09: 1ffff92000022e60
R10: dffffc0000000000 R11: fffff52000022e61 R12: ffff88807fe21c70
R13: dffffc0000000000 R14: ffff888024c29160 R15: ffff88807fe21c70
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4b64ffe00 CR3: 000000007cfa4000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-loop-fix-__list_add_valid-in-loop-driver.patch --]
[-- Type: text/x-patch; name="0001-loop-fix-__list_add_valid-in-loop-driver.patch", Size: 5523 bytes --]

From 4fca4916e323224267fe1d6c8ca332824ebf7808 Mon Sep 17 00:00:00 2001
From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
Date: Mon, 17 Feb 2025 10:40:59 +0800
Subject: [RFC PATCH] loop: fix __list_add_valid in loop driver

Oops reported by syzbot[1] which introduced by commit 3bee991f2b68 of
linux-next(loop: release the lo_work_lock before queue_work). This should
be caused by bellow race scenario and could be fixed by subsituting the
judge if working_pending to list_empty.

mainline before 3bee991f2b68:
T0                                 kworker/u0:1
 loop_queue_work() {                process_one_work() {
  if(!work_pending)                  set_work_pool_and_clear_pending()
   queue_work() {
    set_work_data(WORK_PENDING)
  spin_unlock(worker->lock)
 }				    loop_process_work {
                                      spin_lock(worker->lock)
    				      if(!work_pending) //FAILED HERE
				       list_add(&work->idle_list)

linux-next after 3bee991f2b68:
T0 & kworker/u0:0                  kworker/u0:1
 loop_queue_work() {                process_one_work() {
                                      set_work_pool_and_clear_pending()
  spin_unlock(worker->lock)           loop_process_work() {
                                        spin_lock(worker->lock)
		                        if(!work_pending) //FIRST ADD
                                          list_add(&work->idle_list)
  if(!work_pending)
   queue_work()
    set_work_data(WORK_PENDING)
  spin_unlock(worker->lock)
 }

 process_one_work() {
  set_work_pool_and_clear_pending()
  loop_process_work() {
    spin_lock(worker->lock)
    if(!work_pending) //SECOND ADD
      list_add(&work->idle_list)
        BUG(...)

[1]
list_add double add: new=ffff88807fe21c70, prev=ffff88807fe21c70, next=ffff888024c29160.
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:37!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 1 UID: 0 PID: 12 Comm: kworker/u8:1 Not tainted 6.14.0-rc2-next-20250212-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: loop0 loop_workfn
RIP: 0010:__list_add_valid_or_report+0xa4/0x130 lib/list_debug.c:35
Code: f7 74 11 b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 48 c7 c7 40 e5 60 8c 4c 89 fe 4c 89 e2 4c 89 f1 e8 fd 88 35 fc 90 <0f> 0b 48 c7 c7 40 e3 60 8c e8 ee 88 35 fc 90 0f 0b 48 c7 c7 e0 e3
RSP: 0018:ffffc90000117628 EFLAGS: 00010046
RAX: 0000000000000058 RBX: 1ffff1100ffc438e RCX: 89e05f8d6ffcb000
RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
RBP: 1ffff1100498522d R08: ffffffff819f562c R09: 1ffff92000022e60
R10: dffffc0000000000 R11: fffff52000022e61 R12: ffff88807fe21c70
R13: dffffc0000000000 R14: ffff888024c29160 R15: ffff88807fe21c70
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4b64ffe00 CR3: 000000007cfa4000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __list_add_valid include/linux/list.h:88 [inline]
 __list_add include/linux/list.h:150 [inline]
 list_add_tail include/linux/list.h:183 [inline]
 loop_process_work+0x1f96/0x21c0 drivers/block/loop.c:1977
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317
 worker_thread+0x870/0xd30 kernel/workqueue.c:3398
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__list_add_valid_or_report+0xa4/0x130 lib/list_debug.c:35
Code: f7 74 11 b0 01 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 48 c7 c7 40 e5 60 8c 4c 89 fe 4c 89 e2 4c 89 f1 e8 fd 88 35 fc 90 <0f> 0b 48 c7 c7 40 e3 60 8c e8 ee 88 35 fc 90 0f 0b 48 c7 c7 e0 e3
RSP: 0018:ffffc90000117628 EFLAGS: 00010046
RAX: 0000000000000058 RBX: 1ffff1100ffc438e RCX: 89e05f8d6ffcb000
RDX: 0000000000000000 RSI: 0000000080000001 RDI: 0000000000000000
RBP: 1ffff1100498522d R08: ffffffff819f562c R09: 1ffff92000022e60
R10: dffffc0000000000 R11: fffff52000022e61 R12: ffff88807fe21c70
R13: dffffc0000000000 R14: ffff888024c29160 R15: ffff88807fe21c70
FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff4b64ffe00 CR3: 000000007cfa4000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Reported-by: syzbot+c104904eeb2c0edbdb06@syzkaller.appspotmail.com
Fixes: 3bee991f2b68 ("loop: release the lo_work_lock before queue_work")
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 drivers/block/loop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 68c943a77e41..2bcdd9646ac3 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1972,7 +1972,7 @@ static void loop_process_work(struct loop_worker *worker,
 	 * *and* the worker will not run again which ensures that it
 	 * is safe to free any worker on the idle list
 	 */
-	if (worker && !work_pending(&worker->work)) {
+	if (worker && list_empty(&worker->idle_list)) {
 		worker->last_ran_at = jiffies;
 		list_add_tail(&worker->idle_list, &lo->idle_worker_list);
 		loop_set_timer(lo);
-- 
2.25.1