[v6.1] possible deadlock in kvfree_call_rcu

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syzbot

unread,

Mar 21, 2024, 4:02:28 PMMar 21

to syzkaller...@googlegroups.com

Hello,

syzbot found the following issue on:

HEAD commit: d7543167affd Linux 6.1.82
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=121abffa180000
kernel config: https://syzkaller.appspot.com/x/.config?x=59059e181681c079
dashboard link: https://syzkaller.appspot.com/bug?extid=e5952d44ee3e1993cddf
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/88220954516a/disk-d7543167.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c9062e074717/vmlinux-d7543167.xz
kernel image: https://storage.googleapis.com/syzbot-assets/70391b45a752/bzImage-d7543167.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e5952d...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.82-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/2791 is trying to acquire lock:
ffff8880b9828118 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
ffff8880b9828118 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
ffff8880b9828118 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401

but task is already holding lock:
ffff88806997ba38 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc5/0xc00 kernel/bpf/lpm_trie.c:324

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&trie->lock){-.-.}-{2:2}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
trie_delete_elem+0x90/0x690 kernel/bpf/lpm_trie.c:451
bpf_prog_93cf26cf960a0051+0x42/0x8f
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:600 [inline]
bpf_prog_run include/linux/filter.h:607 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run4+0x253/0x470 kernel/trace/bpf_trace.c:2314
__bpf_trace_mm_page_alloc+0xba/0xe0 include/trace/events/kmem.h:177
trace_mm_page_alloc include/trace/events/kmem.h:177 [inline]
__alloc_pages+0x717/0x770 mm/page_alloc.c:5567
alloc_slab_page+0x6a/0x150 mm/slub.c:1794
allocate_slab mm/slub.c:1939 [inline]
new_slab+0x84/0x2d0 mm/slub.c:1992
___slab_alloc+0xc20/0x1270 mm/slub.c:3180
__slab_alloc mm/slub.c:3279 [inline]
slab_alloc_node mm/slub.c:3364 [inline]
slab_alloc mm/slub.c:3406 [inline]
__kmem_cache_alloc_lru mm/slub.c:3413 [inline]
kmem_cache_alloc+0x1a5/0x2d0 mm/slub.c:3422
kmem_cache_zalloc include/linux/slab.h:682 [inline]
fill_pool lib/debugobjects.c:168 [inline]
debug_objects_fill_pool+0x5fc/0xa10 lib/debugobjects.c:606
debug_object_activate+0x32/0x4e0 lib/debugobjects.c:693
debug_hrtimer_activate kernel/time/hrtimer.c:420 [inline]
debug_activate kernel/time/hrtimer.c:475 [inline]
enqueue_hrtimer+0x30/0x410 kernel/time/hrtimer.c:1084
__run_hrtimer kernel/time/hrtimer.c:1703 [inline]
__hrtimer_run_queues+0x728/0xe50 kernel/time/hrtimer.c:1750
hrtimer_interrupt+0x392/0x980 kernel/time/hrtimer.c:1812
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1095 [inline]
__sysvec_apic_timer_interrupt+0x156/0x580 arch/x86/kernel/apic/apic.c:1112
sysvec_apic_timer_interrupt+0x8c/0xb0 arch/x86/kernel/apic/apic.c:1106
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:653
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0xd4/0x130 kernel/locking/spinlock.c:194
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
__wake_up_common_lock kernel/sched/wait.c:140 [inline]
__wake_up_sync_key+0x121/0x1c0 kernel/sched/wait.c:208
sock_def_readable+0x15b/0x280 net/core/sock.c:3304
__netlink_sendskb net/netlink/af_netlink.c:1273 [inline]
netlink_sendskb+0x8e/0x120 net/netlink/af_netlink.c:1279
netlink_unicast+0x394/0x970 net/netlink/af_netlink.c:1367
netlink_sendmsg+0xa26/0xd60 net/netlink/af_netlink.c:1874
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
____sys_sendmsg+0x5a5/0x8f0 net/socket.c:2514
___sys_sendmsg net/socket.c:2568 [inline]
__sys_sendmsg+0x2a9/0x390 net/socket.c:2597
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (hrtimer_bases.lock){-.-.}-{2:2}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
lock_hrtimer_base kernel/time/hrtimer.c:173 [inline]
hrtimer_start_range_ns+0xd8/0xc50 kernel/time/hrtimer.c:1297
hrtimer_start include/linux/hrtimer.h:420 [inline]
run_page_cache_worker kernel/rcu/tree.c:3292 [inline]
kvfree_call_rcu+0x72b/0x8c0 kernel/rcu/tree.c:3403
rtnl_register_internal+0x489/0x580 net/core/rtnetlink.c:260
rtnl_register+0x32/0x70 net/core/rtnetlink.c:310
ip_rt_init+0x335/0x3c7 net/ipv4/route.c:3768
ip_init+0xa/0x14 net/ipv4/ip_output.c:1767
inet_init+0x2ae/0x3c0 net/ipv4/af_inet.c:2031
do_one_initcall+0x265/0x8f0 init/main.c:1296
do_initcall_level+0x157/0x207 init/main.c:1369
do_initcalls+0x49/0x86 init/main.c:1385
kernel_init_freeable+0x45c/0x60f init/main.c:1624
kernel_init+0x19/0x290 init/main.c:1512
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:307

-> #0 (krc.lock){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401
trie_update_elem+0x808/0xc00 kernel/bpf/lpm_trie.c:385
bpf_map_update_value+0x5cf/0x6f0 kernel/bpf/syscall.c:226
map_update_elem+0x503/0x680 kernel/bpf/syscall.c:1448
__sys_bpf+0x337/0x6c0 kernel/bpf/syscall.c:4993
__do_sys_bpf kernel/bpf/syscall.c:5109 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5107 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5107
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
krc.lock --> hrtimer_bases.lock --> &trie->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&trie->lock);
lock(hrtimer_bases.lock);
lock(&trie->lock);
lock(krc.lock);

*** DEADLOCK ***

2 locks held by syz-executor.0/2791:
#0: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:319 [inline]
#0: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:760 [inline]
#0: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: bpf_map_update_value+0x207/0x6f0 kernel/bpf/syscall.c:225
#1: ffff88806997ba38 (&trie->lock){-.-.}-{2:2}, at: trie_update_elem+0xc5/0xc00 kernel/bpf/lpm_trie.c:324

stack backtrace:
CPU: 0 PID: 2791 Comm: syz-executor.0 Not tainted 6.1.82-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401
trie_update_elem+0x808/0xc00 kernel/bpf/lpm_trie.c:385
bpf_map_update_value+0x5cf/0x6f0 kernel/bpf/syscall.c:226
map_update_elem+0x503/0x680 kernel/bpf/syscall.c:1448
__sys_bpf+0x337/0x6c0 kernel/bpf/syscall.c:4993
__do_sys_bpf kernel/bpf/syscall.c:5109 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5107 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5107
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fabefe7dda9
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:00007fabf0b110c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fabeffabf80 RCX: 00007fabefe7dda9
RDX: 0000000000000020 RSI: 0000000020000380 RDI: 0000000000000002
RBP: 00007fabefeca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fabeffabf80 R15: 00007ffc41fe3db8
</TASK>

---
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See https://goo.gl/tpsmEJ for more information about syzbot.
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If the report is already addressed, let syzbot know by replying with:
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syzbot

unread,

Mar 25, 2024, 7:20:30 PMMar 25

to syzkaller...@googlegroups.com

Hello,

syzbot found the following issue on:

HEAD commit: b95c01af2113 Linux 5.15.152
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10c56479180000
kernel config: https://syzkaller.appspot.com/x/.config?x=b26cb65e5b8ad5c7
dashboard link: https://syzkaller.appspot.com/bug?extid=cb88665052d93c3f0be3

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=11154711180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10863185180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2fc98856fcae/disk-b95c01af.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3186db0dfe08/vmlinux-b95c01af.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0df136a3e808/bzImage-b95c01af.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+cb8866...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected

5.15.152-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor108/3499 is trying to acquire lock:
ffff8880b9a27e78 (krc.lock){....}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:3199 [inline]
ffff8880b9a27e78 (krc.lock){....}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3506 [inline]
ffff8880b9a27e78 (krc.lock){....}-{2:2}, at: kvfree_call_rcu+0x1b5/0x8a0 kernel/rcu/tree.c:3597

but task is already holding lock:

ffff88801ca8c1b8 (&trie->lock){-...}-{2:2}, at: trie_update_elem+0xc5/0xc00 kernel/bpf/lpm_trie.c:323

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&trie->lock){-...}-{2:2}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623

__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162

trie_delete_elem+0x90/0x690 kernel/bpf/lpm_trie.c:450
bpf_prog_2c29ac5cdc6b1842+0x3a/0xf88
bpf_dispatcher_nop_func include/linux/bpf.h:780 [inline]
__bpf_prog_run include/linux/filter.h:625 [inline]
bpf_prog_run include/linux/filter.h:632 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:1880 [inline]
bpf_trace_run3+0x1d1/0x380 kernel/trace/bpf_trace.c:1918
trace_timer_start include/trace/events/timer.h:52 [inline]
enqueue_timer+0x3ae/0x540 kernel/time/timer.c:586
__mod_timer+0x9ca/0xeb0 kernel/time/timer.c:1060
sk_reset_timer+0x1f/0xb0 net/core/sock.c:3125
tcp_event_new_data_sent+0x203/0x360 net/ipv4/tcp_output.c:81
tcp_write_xmit+0x1a0b/0x65f0 net/ipv4/tcp_output.c:2712
__tcp_push_pending_frames+0x90/0x250 net/ipv4/tcp_output.c:2890
tcp_sendmsg_locked+0x315c/0x3a90 net/ipv4/tcp.c:1428
tcp_sendmsg+0x2c/0x40 net/ipv4/tcp.c:1456
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
sock_write_iter+0x39b/0x530 net/socket.c:1079
call_write_iter include/linux/fs.h:2148 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0xacf/0xe50 fs/read_write.c:594
ksys_write+0x1a2/0x2c0 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #1 (&base->lock){-.-.}-{2:2}:
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623

__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162

lock_timer_base+0x120/0x260 kernel/time/timer.c:946
__mod_timer+0x1d6/0xeb0 kernel/time/timer.c:1019
queue_delayed_work_on+0x156/0x250 kernel/workqueue.c:1715
queue_delayed_work include/linux/workqueue.h:527 [inline]
schedule_delayed_work include/linux/workqueue.h:631 [inline]
kvfree_call_rcu+0x50e/0x8a0 kernel/rcu/tree.c:3625
rtnl_register_internal+0x443/0x530 net/core/rtnetlink.c:223
rtnl_register+0x32/0x70 net/core/rtnetlink.c:273
ip_rt_init+0x2e6/0x390 net/ipv4/route.c:3755
ip_init+0xa/0x14 net/ipv4/ip_output.c:1749
inet_init+0x27c/0x38e net/ipv4/af_inet.c:2005
do_one_initcall+0x22b/0x7a0 init/main.c:1299
do_initcall_level+0x157/0x207 init/main.c:1372
do_initcalls+0x49/0x86 init/main.c:1388
kernel_init_freeable+0x425/0x5b5 init/main.c:1612
kernel_init+0x19/0x290 init/main.c:1503
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

-> #0 (krc.lock){....}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:3199 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3506 [inline]
kvfree_call_rcu+0x1b5/0x8a0 kernel/rcu/tree.c:3597
trie_update_elem+0x808/0xc00 kernel/bpf/lpm_trie.c:384
bpf_map_update_value+0x5d7/0x6c0 kernel/bpf/syscall.c:221
generic_map_update_batch+0x54d/0x8b0 kernel/bpf/syscall.c:1399
bpf_map_do_batch+0x4d0/0x620
__sys_bpf+0x55c/0x670
__do_sys_bpf kernel/bpf/syscall.c:4733 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4731 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4731
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

other info that might help us debug this:

Chain exists of:

krc.lock --> &base->lock --> &trie->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&trie->lock);

lock(&base->lock);

lock(&trie->lock);
lock(krc.lock);

*** DEADLOCK ***

2 locks held by syz-executor108/3499:
#0: ffffffff8c91f720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:268
#1: ffff88801ca8c1b8 (&trie->lock){-...}-{2:2}, at: trie_update_elem+0xc5/0xc00 kernel/bpf/lpm_trie.c:323

stack backtrace:
CPU: 0 PID: 3499 Comm: syz-executor108 Not tainted 5.15.152-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106

check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:3199 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3506 [inline]
kvfree_call_rcu+0x1b5/0x8a0 kernel/rcu/tree.c:3597
trie_update_elem+0x808/0xc00 kernel/bpf/lpm_trie.c:384
bpf_map_update_value+0x5d7/0x6c0 kernel/bpf/syscall.c:221
generic_map_update_batch+0x54d/0x8b0 kernel/bpf/syscall.c:1399
bpf_map_do_batch+0x4d0/0x620
__sys_bpf+0x55c/0x670
__do_sys_bpf kernel/bpf/syscall.c:4733 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4731 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4731
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fca39d407e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff502c1c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fff502c1e38 RCX: 00007fca39d407e9
RDX: 0000000000000038 RSI: 0000000020000300 RDI: 000000000000001a
RBP: 00007fca39db3610 R08: 00007fff502c1e38 R09: 00007fff502c1e38
R10: 00007fff502c1e38 R11: 0000000000000246 R12: 0

---
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syzbot

unread,

Apr 1, 2024, 5:45:22 PMApr 1

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: e5cd595e23c1 Linux 6.1.83
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13d9c3b1180000
kernel config: https://syzkaller.appspot.com/x/.config?x=99d0cbbc2b2c7cfd

dashboard link: https://syzkaller.appspot.com/bug?extid=e5952d44ee3e1993cddf
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=133c365e180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17cb19b5180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cd28292a2eef/disk-e5cd595e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e8297fd856b2/vmlinux-e5cd595e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ea8c74634429/bzImage-e5cd595e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e5952d...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected

6.1.83-syzkaller #0 Not tainted
------------------------------------------------------
ksoftirqd/1/21 is trying to acquire lock:
ffff8880b9928118 (krc.lock){..-.}-{2:2}, at: krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
ffff8880b9928118 (krc.lock){..-.}-{2:2}, at: add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
ffff8880b9928118 (krc.lock){..-.}-{2:2}, at: kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401

but task is already holding lock:

ffff888079702a38 (&trie->lock){..-.}-{2:2}, at: trie_delete_elem+0x90/0x690 kernel/bpf/lpm_trie.c:451

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&trie->lock){..-.}-{2:2}:

lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162
trie_delete_elem+0x90/0x690 kernel/bpf/lpm_trie.c:451

0xffffffffa0001db6
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run3+0x231/0x440 kernel/trace/bpf_trace.c:2313
trace_timer_start include/trace/events/timer.h:53 [inline]
enqueue_timer+0x440/0x600 kernel/time/timer.c:609
__mod_timer+0x92b/0xee0
queue_delayed_work_on+0x156/0x250 kernel/workqueue.c:1704
queue_delayed_work include/linux/workqueue.h:527 [inline]
toggle_allocation_gate+0x427/0x480 mm/kfence/core.c:820
process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:307

-> #1 (&base->lock){-.-.}-{2:2}:

lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162

lock_timer_base+0x120/0x260 kernel/time/timer.c:999
__mod_timer+0x1cb/0xee0 kernel/time/timer.c:1072
queue_delayed_work_on+0x156/0x250 kernel/workqueue.c:1704
queue_delayed_work include/linux/workqueue.h:527 [inline]
schedule_delayed_monitor_work kernel/rcu/tree.c:3171 [inline]
kvfree_call_rcu+0x520/0x8c0 kernel/rcu/tree.c:3427

rtnl_register_internal+0x489/0x580 net/core/rtnetlink.c:260
rtnl_register+0x32/0x70 net/core/rtnetlink.c:310
ip_rt_init+0x335/0x3c7 net/ipv4/route.c:3768
ip_init+0xa/0x14 net/ipv4/ip_output.c:1767
inet_init+0x2ae/0x3c0 net/ipv4/af_inet.c:2031

do_one_initcall+0x265/0x8f0 init/main.c:1297
do_initcall_level+0x157/0x207 init/main.c:1370
do_initcalls+0x49/0x86 init/main.c:1386
kernel_init_freeable+0x45c/0x60f init/main.c:1625
kernel_init+0x19/0x290 init/main.c:1513

ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:307

-> #0 (krc.lock){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401

trie_delete_elem+0x520/0x690
bpf_prog_2c29ac5cdc6b1842+0x3a/0x3e
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run3+0x231/0x440 kernel/trace/bpf_trace.c:2313
trace_timer_start include/trace/events/timer.h:53 [inline]
enqueue_timer+0x440/0x600 kernel/time/timer.c:609
__mod_timer+0x92b/0xee0
queue_delayed_work_on+0x156/0x250 kernel/workqueue.c:1704
queue_delayed_work include/linux/workqueue.h:527 [inline]
srcu_funnel_gp_start kernel/rcu/srcutree.c:951 [inline]
srcu_gp_start_if_needed+0xce5/0x1080 kernel/rcu/srcutree.c:1151
rcu_do_batch kernel/rcu/tree.c:2296 [inline]
rcu_core+0xad4/0x17e0 kernel/rcu/tree.c:2556
__do_softirq+0x2e9/0xa4c kernel/softirq.c:571
run_ksoftirqd+0xc1/0x120 kernel/softirq.c:934
smpboot_thread_fn+0x52c/0xa30 kernel/smpboot.c:164
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:307

other info that might help us debug this:

Chain exists of:

krc.lock --> &base->lock --> &trie->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&trie->lock);

lock(&base->lock);

lock(&trie->lock);
lock(krc.lock);

*** DEADLOCK ***

6 locks held by ksoftirqd/1/21:
#0: ffffffff8d12aa00 (rcu_callback){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8d12aa00 (rcu_callback){....}-{0:0}, at: rcu_do_batch kernel/rcu/tree.c:2291 [inline]
#0: ffffffff8d12aa00 (rcu_callback){....}-{0:0}, at: rcu_core+0xa64/0x17e0 kernel/rcu/tree.c:2556
#1: ffffffff8d171228 (tracepoint_srcu){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#1: ffffffff8d171228 (tracepoint_srcu){....}-{0:0}, at: srcu_read_lock include/linux/srcu.h:165 [inline]
#1: ffffffff8d171228 (tracepoint_srcu){....}-{0:0}, at: srcu_gp_start_if_needed+0x17f/0x1080 kernel/rcu/srcutree.c:1094
#2: ffffffff8d170f68 (tracepoint_srcu.lock){....}-{2:2}, at: spin_lock_irqsave_ssp_contention+0x106/0x440 kernel/rcu/srcutree.c:378
#3: ffff8880b9928358 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x62d/0xee0 kernel/time/timer.c:1096
#4: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#4: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#4: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2272 [inline]
#4: ffffffff8d12a940 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run3+0x146/0x440 kernel/trace/bpf_trace.c:2313
#5: ffff888079702a38 (&trie->lock){..-.}-{2:2}, at: trie_delete_elem+0x90/0x690 kernel/bpf/lpm_trie.c:451

stack backtrace:
CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 6.1.83-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024

Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
krc_this_cpu_lock kernel/rcu/tree.c:2990 [inline]
add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3310 [inline]
kvfree_call_rcu+0x1b2/0x8c0 kernel/rcu/tree.c:3401

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