[syzbot] [net?] WARNING: suspicious RCU usage in br_mst_set_state (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8a92980606e3 Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f9eaba980000
kernel config: https://syzkaller.appspot.com/x/.config?x=9a6ac4277fffe3ea
dashboard link: https://syzkaller.appspot.com/bug?extid=9bbe2de1bc9d470eb5fe
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e77750e429bf/disk-8a929806.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/910e4410cf78/vmlinux-8a929806.xz
kernel image: https://storage.googleapis.com/syzbot-assets/85542820b0d5/bzImage-8a929806.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9bbe2d...@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
6.10.0-rc2-syzkaller-00235-g8a92980606e3 #0 Not tainted
-----------------------------
net/bridge/br_private.h:1599 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
4 locks held by syz-executor.1/5374:
#0: ffff888022d50b18 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:144 [inline]
#0: ffff888022d50b18 (&mm->mmap_lock){++++}-{3:3}, at: __mm_populate+0x1b0/0x460 mm/gup.c:2111
#1: ffffc90000a18c00 ((&p->forward_delay_timer)){+.-.}-{0:0}, at: call_timer_fn+0xc0/0x650 kernel/time/timer.c:1789
#2: ffff88805fb2ccb8 (&br->lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
#2: ffff88805fb2ccb8 (&br->lock){+.-.}-{2:2}, at: br_forward_delay_timer_expired+0x50/0x440 net/bridge/br_stp_timer.c:86
#3: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#3: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#3: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: br_mst_set_state+0x171/0x7a0 net/bridge/br_mst.c:105

stack backtrace:
CPU: 1 PID: 5374 Comm: syz-executor.1 Not tainted 6.10.0-rc2-syzkaller-00235-g8a92980606e3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
lockdep_rcu_suspicious+0x221/0x340 kernel/locking/lockdep.c:6712
nbp_vlan_group net/bridge/br_private.h:1599 [inline]
br_mst_set_state+0x29e/0x7a0 net/bridge/br_mst.c:106
br_set_state+0x28a/0x7b0 net/bridge/br_stp.c:47
br_forward_delay_timer_expired+0x176/0x440 net/bridge/br_stp_timer.c:88
call_timer_fn+0x18e/0x650 kernel/time/timer.c:1792
expire_timers kernel/time/timer.c:1843 [inline]
__run_timers kernel/time/timer.c:2417 [inline]
__run_timer_base+0x66a/0x8e0 kernel/time/timer.c:2428
run_timer_base kernel/time/timer.c:2437 [inline]
run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2447
handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
__do_softirq kernel/softirq.c:588 [inline]
invoke_softirq kernel/softirq.c:428 [inline]
__irq_exit_rcu+0xf4/0x1c0 kernel/softirq.c:637
irq_exit_rcu+0x9/0x30 kernel/softirq.c:649
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:87 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:104 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:129 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:161 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x86/0x290 mm/kasan/generic.c:189
Code: 00 fc ff df 4f 8d 3c 31 4c 89 fd 4c 29 dd 48 83 fd 10 7f 29 48 85 ed 0f 84 3e 01 00 00 4c 89 cd 48 f7 d5 48 01 dd 41 80 3b 00 <0f> 85 c9 01 00 00 49 ff c3 48 ff c5 75 ee e9 1e 01 00 00 45 89 dc
RSP: 0018:ffffc90004beec90 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 1ffff9200097dd9c RCX: ffffffff8173cb88
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffffc90004beece0
RBP: ffffffffffffffff R08: ffffc90004beece3 R09: 1ffff9200097dd9c
R10: dffffc0000000000 R11: fffff5200097dd9c R12: 1ffff9200097dd98
R13: ffff8880b9544700 R14: dffffc0000000001 R15: fffff5200097dd9d
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:1301 [inline]
queued_spin_trylock include/asm-generic/qspinlock.h:97 [inline]
do_raw_spin_trylock+0xc8/0x1f0 kernel/locking/spinlock_debug.c:123
__raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline]
_raw_spin_trylock+0x20/0x80 kernel/locking/spinlock.c:138
spin_trylock include/linux/spinlock.h:361 [inline]
rmqueue_pcplist mm/page_alloc.c:2940 [inline]
rmqueue mm/page_alloc.c:2990 [inline]
get_page_from_freelist+0x79f/0x2ee0 mm/page_alloc.c:3399
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4660
alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
shmem_alloc_folio mm/shmem.c:1628 [inline]
shmem_alloc_and_add_folio+0x24d/0xdb0 mm/shmem.c:1668
shmem_get_folio_gfp+0x82d/0x1f50 mm/shmem.c:2055
shmem_fault+0x252/0x6f0 mm/shmem.c:2255
__do_fault+0x135/0x460 mm/memory.c:4562
do_read_fault mm/memory.c:4926 [inline]
do_fault mm/memory.c:5056 [inline]
do_pte_missing mm/memory.c:3903 [inline]
handle_pte_fault+0x3d8d/0x7130 mm/memory.c:5380
__handle_mm_fault mm/memory.c:5523 [inline]
handle_mm_fault+0xfb0/0x19d0 mm/memory.c:5688
faultin_page mm/gup.c:1290 [inline]
__get_user_pages+0x6ef/0x1590 mm/gup.c:1589
populate_vma_page_range+0x264/0x330 mm/gup.c:2029
__mm_populate+0x27a/0x460 mm/gup.c:2132
mm_populate include/linux/mm.h:3464 [inline]
vm_mmap_pgoff+0x2c3/0x3d0 mm/util.c:578
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1686c7cf69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f168799f0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f1686db3f80 RCX: 00007f1686c7cf69
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000000020000000
RBP: 00007f1686cda6fe R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f1686db3f80 R15: 00007ffd6eb2ca48
</TASK>
bridge0: port 2(bridge_slave_1) entered learning state
----------------
Code disassembly (best guess), 3 bytes skipped:
0: df 4f 8d fisttps -0x73(%rdi)
3: 3c 31 cmp $0x31,%al
5: 4c 89 fd mov %r15,%rbp
8: 4c 29 dd sub %r11,%rbp
b: 48 83 fd 10 cmp $0x10,%rbp
f: 7f 29 jg 0x3a
11: 48 85 ed test %rbp,%rbp
14: 0f 84 3e 01 00 00 je 0x158
1a: 4c 89 cd mov %r9,%rbp
1d: 48 f7 d5 not %rbp
20: 48 01 dd add %rbx,%rbp
23: 41 80 3b 00 cmpb $0x0,(%r11)
* 27: 0f 85 c9 01 00 00 jne 0x1f6 <-- trapping instruction
2d: 49 ff c3 inc %r11
30: 48 ff c5 inc %rbp
33: 75 ee jne 0x23
35: e9 1e 01 00 00 jmp 0x158
3a: 45 89 dc mov %r11d,%r12d


---
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[Nikolay Aleksandrov]

On June 8, 2024 8:29:23 PM GMT+03:00, syzbot <syzbot+9bbe2d...@syzkaller.appspotmail.com> wrote:
>Hello,
>
>syzbot found the following issue on:
>
>HEAD commit: 8a92980606e3 Merge tag 'scsi-fixes' of git://git.kernel.or..
>git tree: upstream
>console output: https://syzkaller.appspot.com/x/log.txt?x=14f9eaba980000
>kernel config: https://syzkaller.appspot.com/x/.config?x=9a6ac4277fffe3ea
>dashboard link: https://syzkaller.appspot.com/bug?extid=9bbe2de1bc9d470eb5fe
>compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
>Unfortunately, I don't have any reproducer for this issue yet.
>
>Downloadable assets:
>disk image: https://storage.googleapis.com/syzbot-assets/e77750e429bf/disk-8a929806.raw.xz
>vmlinux: https://storage.googleapis.com/syzbot-assets/910e4410cf78/vmlinux-8a929806.xz
>kernel image: https://storage.googleapis.com/syzbot-assets/85542820b0d5/bzImage-8a929806.xz
>
>IMPORTANT: if you fix the issue, please add the following tag to the commit:

>Reported-by: syzbot+9bbe2de1bc9d470eb5fe@:

Oh, my fix was incomplete, I should've changed the deref helper as well.
I will send a patch tomorrow.

Thanks!