Subject: [syzbot] linux-next boot error: KASAN: out-of-bounds Read in rcu_cblist_dequeue

From: syzbot <[email-masked]>
Date: Thu, 11 Aug 2022 05:43:23 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    40d43a7507e1 Add linux-next specific files for 20220811
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=170595fd080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a5ae8cfa8d7075d1
dashboard link: https://syzkaller.appspot.com/bug?extid=4f473a64b5132e9560d1
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: out-of-bounds in rcu_cblist_dequeue+0xa4/0xe0 kernel/rcu/rcu_segcblist.c:75
Read of size 8 at addr ffffc90004f08000 by task ksoftirqd/1/21

CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.19.0-next-20220811-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:317 [inline]
 print_report.cold+0x59/0x719 mm/kasan/report.c:433
 kasan_report+0xb1/0x1e0 mm/kasan/report.c:495
 rcu_cblist_dequeue+0xa4/0xe0 kernel/rcu/rcu_segcblist.c:75
 rcu_do_batch kernel/rcu/tree.c:2234 [inline]
 rcu_core+0x735/0x1890 kernel/rcu/tree.c:2505
 __do_softirq+0x1d3/0x9c6 kernel/softirq.c:571
 run_ksoftirqd kernel/softirq.c:934 [inline]
 run_ksoftirqd+0x2d/0x60 kernel/softirq.c:926
 smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>

The buggy address belongs to the virtual mapping at
 [ffffc90004f08000, ffffc90004f11000) created by:
 kernel_clone+0xe7/0xab0 kernel/fork.c:2675

The buggy address belongs to the physical page:
page:ffffea00007ed940 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1fb65
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_NOWARN|__GFP_ZERO), pid 11, tgid 11 (kworker/u4:1), ts 8261677515, free_ts 0
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x109b/0x2cd0 mm/page_alloc.c:4283
 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5507
 __alloc_pages_bulk+0x9fc/0x15a0 mm/page_alloc.c:5455
 alloc_pages_bulk_array_mempolicy+0x1b3/0x360 mm/mempolicy.c:2365
 vm_area_alloc_pages mm/vmalloc.c:2930 [inline]
 __vmalloc_area_node mm/vmalloc.c:3026 [inline]
 __vmalloc_node_range+0x576/0x13a0 mm/vmalloc.c:3196
 alloc_thread_stack_node kernel/fork.c:312 [inline]
 dup_task_struct kernel/fork.c:977 [inline]
 copy_process+0x13cd/0x7120 kernel/fork.c:2088
 kernel_clone+0xe7/0xab0 kernel/fork.c:2675
 user_mode_thread+0xad/0xe0 kernel/fork.c:2744
 call_usermodehelper_exec_work kernel/umh.c:174 [inline]
 call_usermodehelper_exec_work+0xcc/0x180 kernel/umh.c:160
 process_one_work+0x991/0x1610 kernel/workqueue.c:2289
 worker_thread+0x665/0x1080 kernel/workqueue.c:2436
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page_owner free stack trace missing

Memory state around the buggy address:
 ffffc90004f07f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004f07f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90004f08000: 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                   ^
 ffffc90004f08080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90004f08100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
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 [email-masked].

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