* [syzbot] [bpf?] [net?] possible deadlock in rcu_report_exp_cpu_mult
@ 2024-03-18 10:07 syzbot
2024-03-23 5:42 ` [PATCH] bpf, sockmap: fix " Edward Adam Davis
0 siblings, 1 reply; 8+ messages in thread
From: syzbot @ 2024-03-18 10:07 UTC (permalink / raw)
To: 42.hyeyoo, andrii, ast, bpf, daniel, davem, edumazet, jakub,
john.fastabend, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
Hello,
syzbot found the following issue on:
HEAD commit: ea80e3ed09ab net: ethernet: mtk_eth_soc: fix PPE hanging i..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=1249daa5180000
kernel config: https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=c4f4d25859c2e5859988
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=17fd8c81180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1795afc1180000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4c6c49a7ef5c/disk-ea80e3ed.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/242942b30f2d/vmlinux-ea80e3ed.xz
kernel image: https://storage.googleapis.com/syzbot-assets/74dcc2059655/bzImage-ea80e3ed.xz
The issue was bisected to:
commit ee042be16cb455116d0fe99b77c6bc8baf87c8c6
Author: Namhyung Kim <namhyung@kernel.org>
Date: Tue Mar 22 18:57:09 2022 +0000
locking: Apply contention tracepoints in the slow path
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1702c2a5180000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1482c2a5180000
console output: https://syzkaller.appspot.com/x/log.txt?x=1082c2a5180000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com
Fixes: ee042be16cb4 ("locking: Apply contention tracepoints in the slow path")
=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
6.8.0-syzkaller-05221-gea80e3ed09ab #0 Not tainted
-----------------------------------------------------
rcu_exp_gp_kthr/18 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
and this task is already holding:
ffffffff8e136558 (rcu_node_0){-.-.}-{2:2}, at: sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
which would create a new lock dependency:
(rcu_node_0){-.-.}-{2:2} -> (&htab->buckets[i].lock){+...}-{2:2}
but this new dependency connects a HARDIRQ-irq-safe lock:
(rcu_node_0){-.-.}-{2:2}
... which became HARDIRQ-irq-safe at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
rcu_report_exp_cpu_mult+0x27/0x2f0 kernel/rcu/tree_exp.h:238
csd_do_func kernel/smp.c:133 [inline]
__flush_smp_call_function_queue+0xb2e/0x15b0 kernel/smp.c:542
__sysvec_call_function_single+0xa8/0x3e0 arch/x86/kernel/smp.c:271
instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
sysvec_call_function_single+0x9e/0xc0 arch/x86/kernel/smp.c:266
asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
__sanitizer_cov_trace_switch+0x90/0x120
update_event_printk kernel/trace/trace_events.c:2750 [inline]
trace_event_eval_update+0x311/0xf90 kernel/trace/trace_events.c:2922
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
to a HARDIRQ-irq-unsafe lock:
(&htab->buckets[i].lock){+...}-{2:2}
... which became HARDIRQ-irq-unsafe at:
...
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
0xffffffffa0001b0e
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
futex_cleanup_begin kernel/futex/core.c:1091 [inline]
futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
exit_mm_release+0x1a/0x30 kernel/fork.c:1652
exit_mm+0xb0/0x310 kernel/exit.c:542
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&htab->buckets[i].lock);
local_irq_disable();
lock(rcu_node_0);
lock(&htab->buckets[i].lock);
<Interrupt>
lock(rcu_node_0);
*** DEADLOCK ***
2 locks held by rcu_exp_gp_kthr/18:
#0: ffffffff8e136558 (rcu_node_0){-.-.}-{2:2}, at: sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
#1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x114/0x420 kernel/trace/bpf_trace.c:2420
the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (rcu_node_0){-.-.}-{2:2} {
IN-HARDIRQ-W at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
rcu_report_exp_cpu_mult+0x27/0x2f0 kernel/rcu/tree_exp.h:238
csd_do_func kernel/smp.c:133 [inline]
__flush_smp_call_function_queue+0xb2e/0x15b0 kernel/smp.c:542
__sysvec_call_function_single+0xa8/0x3e0 arch/x86/kernel/smp.c:271
instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
sysvec_call_function_single+0x9e/0xc0 arch/x86/kernel/smp.c:266
asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
__sanitizer_cov_trace_switch+0x90/0x120
update_event_printk kernel/trace/trace_events.c:2750 [inline]
trace_event_eval_update+0x311/0xf90 kernel/trace/trace_events.c:2922
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
IN-SOFTIRQ-W at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
rcu_report_qs_rdp kernel/rcu/tree.c:2018 [inline]
rcu_check_quiescent_state kernel/rcu/tree.c:2100 [inline]
rcu_core+0x3ae/0x1830 kernel/rcu/tree.c:2455
__do_softirq+0x2bc/0x943 kernel/softirq.c:554
invoke_softirq kernel/softirq.c:428 [inline]
__irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
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
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
unwind_next_frame+0x1d8e/0x2a00 arch/x86/kernel/unwind_orc.c:665
arch_stack_walk+0x151/0x1b0 arch/x86/kernel/stacktrace.c:25
stack_trace_save+0x118/0x1d0 kernel/stacktrace.c:122
save_stack+0xfb/0x1f0 mm/page_owner.c:129
__set_page_owner+0x29/0x380 mm/page_owner.c:195
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1533
prep_new_page mm/page_alloc.c:1540 [inline]
get_page_from_freelist+0x33ea/0x3580 mm/page_alloc.c:3311
__alloc_pages+0x256/0x680 mm/page_alloc.c:4569
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2190
allocate_slab mm/slub.c:2354 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2407
___slab_alloc+0xd1b/0x13e0 mm/slub.c:3540
__slab_alloc mm/slub.c:3625 [inline]
__slab_alloc_node mm/slub.c:3678 [inline]
slab_alloc_node mm/slub.c:3850 [inline]
kmalloc_trace+0x267/0x360 mm/slub.c:4007
kmalloc include/linux/slab.h:590 [inline]
kzalloc include/linux/slab.h:711 [inline]
ddebug_add_module+0x88/0x800 lib/dynamic_debug.c:1240
dynamic_debug_init+0x205/0x5a0 lib/dynamic_debug.c:1446
do_one_initcall+0x238/0x830 init/main.c:1241
do_pre_smp_initcalls+0x57/0xa0 init/main.c:1347
kernel_init_freeable+0x40d/0x5d0 init/main.c:1546
kernel_init+0x1d/0x2a0 init/main.c:1446
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
INITIAL USE at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
rcutree_prepare_cpu+0x71/0x640 kernel/rcu/tree.c:4484
rcu_init+0x9b/0x140 kernel/rcu/tree.c:5224
start_kernel+0x1f7/0x500 init/main.c:969
x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:509
x86_64_start_kernel+0x99/0xa0 arch/x86/kernel/head64.c:490
common_startup_64+0x13e/0x147
}
... key at: [<ffffffff945012e0>] rcu_init_one.rcu_node_class+0x0/0x20
the dependencies between the lock to be acquired
and HARDIRQ-irq-unsafe lock:
-> (&htab->buckets[i].lock){+...}-{2:2} {
HARDIRQ-ON-W at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
0xffffffffa0001b0e
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
futex_cleanup_begin kernel/futex/core.c:1091 [inline]
futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
exit_mm_release+0x1a/0x30 kernel/fork.c:1652
exit_mm+0xb0/0x310 kernel/exit.c:542
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
INITIAL USE at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
0xffffffffa0001b0e
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
futex_cleanup_begin kernel/futex/core.c:1091 [inline]
futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
exit_mm_release+0x1a/0x30 kernel/fork.c:1652
exit_mm+0xb0/0x310 kernel/exit.c:542
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
}
... key at: [<ffffffff94882300>] sock_hash_alloc.__key+0x0/0x20
... acquired at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
bpf_prog_43221478a22f23b5+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xf6/0x120 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x939/0xc60 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162
sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:516 [inline]
synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:570 [inline]
rcu_exp_wait_wake kernel/rcu/tree_exp.h:641 [inline]
rcu_exp_sel_wait_wake+0x628/0x1df0 kernel/rcu/tree_exp.h:675
kthread_worker_fn+0x4bf/0xab0 kernel/kthread.c:841
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
stack backtrace:
CPU: 1 PID: 18 Comm: rcu_exp_gp_kthr Not tainted 6.8.0-syzkaller-05221-gea80e3ed09ab #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+0x1e7/0x2e0 lib/dump_stack.c:106
print_bad_irq_dependency kernel/locking/lockdep.c:2626 [inline]
check_irq_usage kernel/locking/lockdep.c:2865 [inline]
check_prev_add kernel/locking/lockdep.c:3138 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x4dc7/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
bpf_prog_43221478a22f23b5+0x42/0x46
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xf6/0x120 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x939/0xc60 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:584 [inline]
queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x272/0x370 kernel/locking/spinlock_debug.c:116
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0xe1/0x120 kernel/locking/spinlock.c:162
sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:516 [inline]
synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:570 [inline]
rcu_exp_wait_wake kernel/rcu/tree_exp.h:641 [inline]
rcu_exp_sel_wait_wake+0x628/0x1df0 kernel/rcu/tree_exp.h:675
kthread_worker_fn+0x4bf/0xab0 kernel/kthread.c:841
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
</TASK>
------------[ cut here ]------------
raw_local_irq_restore() called with IRQs enabled
WARNING: CPU: 1 PID: 18 at kernel/locking/irqflag-debug.c:10 warn_bogus_irq_restore+0x29/0x40 kernel/locking/irqflag-debug.c:10
Modules linked in:
CPU: 1 PID: 18 Comm: rcu_exp_gp_kthr Not tainted 6.8.0-syzkaller-05221-gea80e3ed09ab #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
RIP: 0010:warn_bogus_irq_restore+0x29/0x40 kernel/locking/irqflag-debug.c:10
Code: 90 f3 0f 1e fa 90 80 3d 9e 69 01 04 00 74 06 90 c3 cc cc cc cc c6 05 8f 69 01 04 01 90 48 c7 c7 20 ba aa 8b e8 f8 e5 e7 f5 90 <0f> 0b 90 90 90 c3 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 0f 1f
RSP: 0018:ffffc90000177bb8 EFLAGS: 00010246
RAX: bd04dc17ab040900 RBX: 1ffff9200002ef7c RCX: ffff8880172c1e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000177c48 R08: ffffffff8157cc12 R09: 1ffff9200002eecc
R10: dffffc0000000000 R11: fffff5200002eecd R12: dffffc0000000000
R13: 1ffff9200002ef78 R14: ffffc90000177be0 R15: 0000000000000246
FS: 0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f6d95bcb0d0 CR3: 000000002098e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
_raw_spin_unlock_irqrestore+0x120/0x140 kernel/locking/spinlock.c:194
sync_rcu_exp_done_unlocked+0xdb/0x140 kernel/rcu/tree_exp.h:171
synchronize_rcu_expedited_wait_once kernel/rcu/tree_exp.h:516 [inline]
synchronize_rcu_expedited_wait kernel/rcu/tree_exp.h:570 [inline]
rcu_exp_wait_wake kernel/rcu/tree_exp.h:641 [inline]
rcu_exp_sel_wait_wake+0x628/0x1df0 kernel/rcu/tree_exp.h:675
kthread_worker_fn+0x4bf/0xab0 kernel/kthread.c:841
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
</TASK>
---
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 syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-18 10:07 [syzbot] [bpf?] [net?] possible deadlock in rcu_report_exp_cpu_mult syzbot
@ 2024-03-23 5:42 ` Edward Adam Davis
2024-03-23 7:08 ` Alexei Starovoitov
0 siblings, 1 reply; 8+ messages in thread
From: Edward Adam Davis @ 2024-03-23 5:42 UTC (permalink / raw)
To: syzbot+c4f4d25859c2e5859988
Cc: 42.hyeyoo, andrii, ast, bpf, daniel, davem, edumazet, jakub,
john.fastabend, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
[Syzbot reported]
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
6.8.0-syzkaller-05221-gea80e3ed09ab #0 Not tainted
-----------------------------------------------------
rcu_exp_gp_kthr/18 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
and this task is already holding:
ffffffff8e136558 (rcu_node_0){-.-.}-{2:2}, at: sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
which would create a new lock dependency:
(rcu_node_0){-.-.}-{2:2} -> (&htab->buckets[i].lock){+...}-{2:2}
but this new dependency connects a HARDIRQ-irq-safe lock:
(rcu_node_0){-.-.}-{2:2}
... which became HARDIRQ-irq-safe at:
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
rcu_report_exp_cpu_mult+0x27/0x2f0 kernel/rcu/tree_exp.h:238
csd_do_func kernel/smp.c:133 [inline]
__flush_smp_call_function_queue+0xb2e/0x15b0 kernel/smp.c:542
__sysvec_call_function_single+0xa8/0x3e0 arch/x86/kernel/smp.c:271
instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
sysvec_call_function_single+0x9e/0xc0 arch/x86/kernel/smp.c:266
asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
__sanitizer_cov_trace_switch+0x90/0x120
update_event_printk kernel/trace/trace_events.c:2750 [inline]
trace_event_eval_update+0x311/0xf90 kernel/trace/trace_events.c:2922
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
to a HARDIRQ-irq-unsafe lock:
(&htab->buckets[i].lock){+...}-{2:2}
... which became HARDIRQ-irq-unsafe at:
...
lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
0xffffffffa0001b0e
bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
__bpf_prog_run include/linux/filter.h:657 [inline]
bpf_prog_run include/linux/filter.h:664 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:617 [inline]
__mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
futex_cleanup_begin kernel/futex/core.c:1091 [inline]
futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
exit_mm_release+0x1a/0x30 kernel/fork.c:1652
exit_mm+0xb0/0x310 kernel/exit.c:542
do_exit+0x99e/0x27e0 kernel/exit.c:865
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
__do_sys_exit_group kernel/exit.c:1038 [inline]
__se_sys_exit_group kernel/exit.c:1036 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6d/0x75
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&htab->buckets[i].lock);
local_irq_disable();
lock(rcu_node_0);
lock(&htab->buckets[i].lock);
<Interrupt>
lock(rcu_node_0);
*** DEADLOCK ***
[Fix]
Ensure that the context interrupt state is the same before and after using the
bucket->lock.
Reported-and-tested-by: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
net/core/sock_map.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 27d733c0f65e..ae8f81b26e16 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -932,11 +932,12 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
struct bpf_shtab_bucket *bucket;
struct bpf_shtab_elem *elem;
int ret = -ENOENT;
+ unsigned long flags;
hash = sock_hash_bucket_hash(key, key_size);
bucket = sock_hash_select_bucket(htab, hash);
- spin_lock_bh(&bucket->lock);
+ spin_lock_irqsave(&bucket->lock, flags);
elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
if (elem) {
hlist_del_rcu(&elem->node);
@@ -944,7 +945,7 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
sock_hash_free_elem(htab, elem);
ret = 0;
}
- spin_unlock_bh(&bucket->lock);
+ spin_unlock_irqrestore(&bucket->lock, flags);
return ret;
}
@@ -1136,6 +1137,7 @@ static void sock_hash_free(struct bpf_map *map)
struct bpf_shtab_elem *elem;
struct hlist_node *node;
int i;
+ unsigned long flags;
/* After the sync no updates or deletes will be in-flight so it
* is safe to walk map and remove entries without risking a race
@@ -1151,11 +1153,11 @@ static void sock_hash_free(struct bpf_map *map)
* exists, psock exists and holds a ref to socket. That
* lets us to grab a socket ref too.
*/
- spin_lock_bh(&bucket->lock);
+ spin_lock_irqsave(&bucket->lock, flags);
hlist_for_each_entry(elem, &bucket->head, node)
sock_hold(elem->sk);
hlist_move_list(&bucket->head, &unlink_list);
- spin_unlock_bh(&bucket->lock);
+ spin_unlock_irqrestore(&bucket->lock, flags);
/* Process removed entries out of atomic context to
* block for socket lock before deleting the psock's
--
2.43.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-23 5:42 ` [PATCH] bpf, sockmap: fix " Edward Adam Davis
@ 2024-03-23 7:08 ` Alexei Starovoitov
2024-03-25 12:23 ` Jakub Sitnicki
0 siblings, 1 reply; 8+ messages in thread
From: Alexei Starovoitov @ 2024-03-23 7:08 UTC (permalink / raw)
To: Edward Adam Davis, John Fastabend
Cc: syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, jakub, kafai, kpsingh, kuba, linux-kernel,
namhyung, netdev, pabeni, peterz, songliubraving, syzkaller-bugs,
yhs
John,
please review.
It seems this bug was causing multiple syzbot reports.
On Fri, Mar 22, 2024 at 10:42 PM Edward Adam Davis <eadavis@qq.com> wrote:
>
> [Syzbot reported]
> WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
> 6.8.0-syzkaller-05221-gea80e3ed09ab #0 Not tainted
> -----------------------------------------------------
> rcu_exp_gp_kthr/18 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
> ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
> ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
>
> and this task is already holding:
> ffffffff8e136558 (rcu_node_0){-.-.}-{2:2}, at: sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
> which would create a new lock dependency:
> (rcu_node_0){-.-.}-{2:2} -> (&htab->buckets[i].lock){+...}-{2:2}
>
> but this new dependency connects a HARDIRQ-irq-safe lock:
> (rcu_node_0){-.-.}-{2:2}
>
> ... which became HARDIRQ-irq-safe at:
> lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
> rcu_report_exp_cpu_mult+0x27/0x2f0 kernel/rcu/tree_exp.h:238
> csd_do_func kernel/smp.c:133 [inline]
> __flush_smp_call_function_queue+0xb2e/0x15b0 kernel/smp.c:542
> __sysvec_call_function_single+0xa8/0x3e0 arch/x86/kernel/smp.c:271
> instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
> sysvec_call_function_single+0x9e/0xc0 arch/x86/kernel/smp.c:266
> asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
> __sanitizer_cov_trace_switch+0x90/0x120
> update_event_printk kernel/trace/trace_events.c:2750 [inline]
> trace_event_eval_update+0x311/0xf90 kernel/trace/trace_events.c:2922
> process_one_work kernel/workqueue.c:3254 [inline]
> process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
> worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
> kthread+0x2f0/0x390 kernel/kthread.c:388
> ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
>
> to a HARDIRQ-irq-unsafe lock:
> (&htab->buckets[i].lock){+...}-{2:2}
>
> ... which became HARDIRQ-irq-unsafe at:
> ...
> lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
> __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
> _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
> spin_lock_bh include/linux/spinlock.h:356 [inline]
> sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
> 0xffffffffa0001b0e
> bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
> __bpf_prog_run include/linux/filter.h:657 [inline]
> bpf_prog_run include/linux/filter.h:664 [inline]
> __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
> bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
> trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
> __mutex_lock_common kernel/locking/mutex.c:617 [inline]
> __mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
> futex_cleanup_begin kernel/futex/core.c:1091 [inline]
> futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
> exit_mm_release+0x1a/0x30 kernel/fork.c:1652
> exit_mm+0xb0/0x310 kernel/exit.c:542
> do_exit+0x99e/0x27e0 kernel/exit.c:865
> do_group_exit+0x207/0x2c0 kernel/exit.c:1027
> __do_sys_exit_group kernel/exit.c:1038 [inline]
> __se_sys_exit_group kernel/exit.c:1036 [inline]
> __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
> do_syscall_64+0xfb/0x240
> entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> other info that might help us debug this:
>
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&htab->buckets[i].lock);
> local_irq_disable();
> lock(rcu_node_0);
> lock(&htab->buckets[i].lock);
> <Interrupt>
> lock(rcu_node_0);
>
> *** DEADLOCK ***
> [Fix]
> Ensure that the context interrupt state is the same before and after using the
> bucket->lock.
>
> Reported-and-tested-by: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> net/core/sock_map.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 27d733c0f65e..ae8f81b26e16 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -932,11 +932,12 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
> struct bpf_shtab_bucket *bucket;
> struct bpf_shtab_elem *elem;
> int ret = -ENOENT;
> + unsigned long flags;
>
> hash = sock_hash_bucket_hash(key, key_size);
> bucket = sock_hash_select_bucket(htab, hash);
>
> - spin_lock_bh(&bucket->lock);
> + spin_lock_irqsave(&bucket->lock, flags);
> elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
> if (elem) {
> hlist_del_rcu(&elem->node);
> @@ -944,7 +945,7 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
> sock_hash_free_elem(htab, elem);
> ret = 0;
> }
> - spin_unlock_bh(&bucket->lock);
> + spin_unlock_irqrestore(&bucket->lock, flags);
> return ret;
> }
>
> @@ -1136,6 +1137,7 @@ static void sock_hash_free(struct bpf_map *map)
> struct bpf_shtab_elem *elem;
> struct hlist_node *node;
> int i;
> + unsigned long flags;
>
> /* After the sync no updates or deletes will be in-flight so it
> * is safe to walk map and remove entries without risking a race
> @@ -1151,11 +1153,11 @@ static void sock_hash_free(struct bpf_map *map)
> * exists, psock exists and holds a ref to socket. That
> * lets us to grab a socket ref too.
> */
> - spin_lock_bh(&bucket->lock);
> + spin_lock_irqsave(&bucket->lock, flags);
> hlist_for_each_entry(elem, &bucket->head, node)
> sock_hold(elem->sk);
> hlist_move_list(&bucket->head, &unlink_list);
> - spin_unlock_bh(&bucket->lock);
> + spin_unlock_irqrestore(&bucket->lock, flags);
>
> /* Process removed entries out of atomic context to
> * block for socket lock before deleting the psock's
> --
> 2.43.0
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-23 7:08 ` Alexei Starovoitov
@ 2024-03-25 12:23 ` Jakub Sitnicki
2024-03-25 13:49 ` Jakub Sitnicki
2024-03-26 22:15 ` Jakub Sitnicki
0 siblings, 2 replies; 8+ messages in thread
From: Jakub Sitnicki @ 2024-03-25 12:23 UTC (permalink / raw)
To: Alexei Starovoitov, Edward Adam Davis, John Fastabend
Cc: syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
On Sat, Mar 23, 2024 at 12:08 AM -07, Alexei Starovoitov wrote:
> John,
> please review.
> It seems this bug was causing multiple syzbot reports.
Any chance we could disallow mutating sockhash from interrupt context?
If that is not an option, then this looks like a good start of a fix.
But we also need to cover sock_map_unref->sock_sock_map_del_link called
from sock_hash_delete_elem. It also grabs a spin lock.
Also, sockhash is not the only affected map type. I see we're grabbing a
spin lock in ->map_delete_elem without disabling interrupts as well in:
- sock_map_delete_elem
- reuseport_array_delete_elem
- xsk_map_delete_elem
> On Fri, Mar 22, 2024 at 10:42 PM Edward Adam Davis <eadavis@qq.com> wrote:
>>
>> [Syzbot reported]
>> WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
>> 6.8.0-syzkaller-05221-gea80e3ed09ab #0 Not tainted
>> -----------------------------------------------------
>> rcu_exp_gp_kthr/18 [HC0[0]:SC0[2]:HE0:SE0] is trying to acquire:
>> ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
>> ffff88802b5ab020 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
>>
>> and this task is already holding:
>> ffffffff8e136558 (rcu_node_0){-.-.}-{2:2}, at: sync_rcu_exp_done_unlocked+0xe/0x140 kernel/rcu/tree_exp.h:169
>> which would create a new lock dependency:
>> (rcu_node_0){-.-.}-{2:2} -> (&htab->buckets[i].lock){+...}-{2:2}
>>
>> but this new dependency connects a HARDIRQ-irq-safe lock:
>> (rcu_node_0){-.-.}-{2:2}
>>
>> ... which became HARDIRQ-irq-safe at:
>> lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>> _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
>> rcu_report_exp_cpu_mult+0x27/0x2f0 kernel/rcu/tree_exp.h:238
>> csd_do_func kernel/smp.c:133 [inline]
>> __flush_smp_call_function_queue+0xb2e/0x15b0 kernel/smp.c:542
>> __sysvec_call_function_single+0xa8/0x3e0 arch/x86/kernel/smp.c:271
>> instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
>> sysvec_call_function_single+0x9e/0xc0 arch/x86/kernel/smp.c:266
>> asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
>> __sanitizer_cov_trace_switch+0x90/0x120
>> update_event_printk kernel/trace/trace_events.c:2750 [inline]
>> trace_event_eval_update+0x311/0xf90 kernel/trace/trace_events.c:2922
>> process_one_work kernel/workqueue.c:3254 [inline]
>> process_scheduled_works+0xa00/0x1770 kernel/workqueue.c:3335
>> worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
>> kthread+0x2f0/0x390 kernel/kthread.c:388
>> ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243
>>
>> to a HARDIRQ-irq-unsafe lock:
>> (&htab->buckets[i].lock){+...}-{2:2}
>>
>> ... which became HARDIRQ-irq-unsafe at:
>> ...
>> lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
>> __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
>> _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
>> spin_lock_bh include/linux/spinlock.h:356 [inline]
>> sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
>> 0xffffffffa0001b0e
>> bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>> __bpf_prog_run include/linux/filter.h:657 [inline]
>> bpf_prog_run include/linux/filter.h:664 [inline]
>> __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>> bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
>> trace_contention_end+0xd7/0x100 include/trace/events/lock.h:122
>> __mutex_lock_common kernel/locking/mutex.c:617 [inline]
>> __mutex_lock+0x2e5/0xd70 kernel/locking/mutex.c:752
>> futex_cleanup_begin kernel/futex/core.c:1091 [inline]
>> futex_exit_release+0x34/0x1f0 kernel/futex/core.c:1143
>> exit_mm_release+0x1a/0x30 kernel/fork.c:1652
>> exit_mm+0xb0/0x310 kernel/exit.c:542
>> do_exit+0x99e/0x27e0 kernel/exit.c:865
>> do_group_exit+0x207/0x2c0 kernel/exit.c:1027
>> __do_sys_exit_group kernel/exit.c:1038 [inline]
>> __se_sys_exit_group kernel/exit.c:1036 [inline]
>> __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
>> do_syscall_64+0xfb/0x240
>> entry_SYSCALL_64_after_hwframe+0x6d/0x75
>>
>> other info that might help us debug this:
>>
>> Possible interrupt unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(&htab->buckets[i].lock);
>> local_irq_disable();
>> lock(rcu_node_0);
>> lock(&htab->buckets[i].lock);
>> <Interrupt>
>> lock(rcu_node_0);
>>
>> *** DEADLOCK ***
>> [Fix]
>> Ensure that the context interrupt state is the same before and after using the
>> bucket->lock.
>>
>> Reported-and-tested-by: syzbot+c4f4d25859c2e5859988@syzkaller.appspotmail.com
>> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
>> ---
>> net/core/sock_map.c | 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
>> index 27d733c0f65e..ae8f81b26e16 100644
>> --- a/net/core/sock_map.c
>> +++ b/net/core/sock_map.c
>> @@ -932,11 +932,12 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
>> struct bpf_shtab_bucket *bucket;
>> struct bpf_shtab_elem *elem;
>> int ret = -ENOENT;
>> + unsigned long flags;
>>
>> hash = sock_hash_bucket_hash(key, key_size);
>> bucket = sock_hash_select_bucket(htab, hash);
>>
>> - spin_lock_bh(&bucket->lock);
>> + spin_lock_irqsave(&bucket->lock, flags);
>> elem = sock_hash_lookup_elem_raw(&bucket->head, hash, key, key_size);
>> if (elem) {
>> hlist_del_rcu(&elem->node);
>> @@ -944,7 +945,7 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
>> sock_hash_free_elem(htab, elem);
>> ret = 0;
>> }
>> - spin_unlock_bh(&bucket->lock);
>> + spin_unlock_irqrestore(&bucket->lock, flags);
>> return ret;
>> }
>>
>> @@ -1136,6 +1137,7 @@ static void sock_hash_free(struct bpf_map *map)
>> struct bpf_shtab_elem *elem;
>> struct hlist_node *node;
>> int i;
>> + unsigned long flags;
>>
>> /* After the sync no updates or deletes will be in-flight so it
>> * is safe to walk map and remove entries without risking a race
>> @@ -1151,11 +1153,11 @@ static void sock_hash_free(struct bpf_map *map)
>> * exists, psock exists and holds a ref to socket. That
>> * lets us to grab a socket ref too.
>> */
>> - spin_lock_bh(&bucket->lock);
>> + spin_lock_irqsave(&bucket->lock, flags);
>> hlist_for_each_entry(elem, &bucket->head, node)
>> sock_hold(elem->sk);
>> hlist_move_list(&bucket->head, &unlink_list);
>> - spin_unlock_bh(&bucket->lock);
>> + spin_unlock_irqrestore(&bucket->lock, flags);
>>
>> /* Process removed entries out of atomic context to
>> * block for socket lock before deleting the psock's
>> --
>> 2.43.0
>>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-25 12:23 ` Jakub Sitnicki
@ 2024-03-25 13:49 ` Jakub Sitnicki
2024-03-29 5:29 ` John Fastabend
2024-03-26 22:15 ` Jakub Sitnicki
1 sibling, 1 reply; 8+ messages in thread
From: Jakub Sitnicki @ 2024-03-25 13:49 UTC (permalink / raw)
To: Alexei Starovoitov, Edward Adam Davis, John Fastabend
Cc: syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote:
[...]
> But we also need to cover sock_map_unref->sock_sock_map_del_link called
> from sock_hash_delete_elem. It also grabs a spin lock.
On second look, no need to disable interrupts in
sock_map_unref->sock_sock_map_del_link. Call is enclosed in the critical
section in sock_hash_delete_elem that has been updated.
I have a question, though, why are we patching sock_hash_free? It
doesn't get called unless there are no more existing users of the BPF
map. So nothing can mutate it from interrupt context.
[...]
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-25 12:23 ` Jakub Sitnicki
2024-03-25 13:49 ` Jakub Sitnicki
@ 2024-03-26 22:15 ` Jakub Sitnicki
2024-03-29 15:52 ` Shung-Hsi Yu
1 sibling, 1 reply; 8+ messages in thread
From: Jakub Sitnicki @ 2024-03-26 22:15 UTC (permalink / raw)
To: Alexei Starovoitov, Edward Adam Davis, John Fastabend
Cc: syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote:
> On Sat, Mar 23, 2024 at 12:08 AM -07, Alexei Starovoitov wrote:
>> It seems this bug was causing multiple syzbot reports.
> Any chance we could disallow mutating sockhash from interrupt context?
I've been playing with the repro from one of the other reports:
https://lore.kernel.org/all/CABOYnLzaRiZ+M1v7dPaeObnj_=S4JYmWbgrXaYsyBbWh=553vQ@mail.gmail.com/
syzkaller workload is artificial. So, if we can avoid it, I'd rather not
support modifying sockmap/sockhash in contexts where irqs are disabled,
and lock safety rules are stricter than what we abide to today.
Ideally, we allow task and softirq contexts with irqs enabled (so no
tracing progs attached to timer tick, which syzcaller is using as corpus
here). Otherwise, we will have to cover for that in selftests.
I'm thinking about a restriction like:
---8<---
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 27d733c0f65e..3692f7256dd6 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -907,6 +907,7 @@ static void sock_hash_delete_from_link(struct bpf_map *map, struct sock *sk,
struct bpf_shtab_elem *elem_probe, *elem = link_raw;
struct bpf_shtab_bucket *bucket;
+ WARN_ON_ONCE(irqs_disabled());
WARN_ON_ONCE(!rcu_read_lock_held());
bucket = sock_hash_select_bucket(htab, elem->hash);
@@ -933,6 +934,10 @@ static long sock_hash_delete_elem(struct bpf_map *map, void *key)
struct bpf_shtab_elem *elem;
int ret = -ENOENT;
+ /* Can't run. We don't play nice with hardirq-safe locks. */
+ if (irqs_disabled())
+ return -EOPNOTSUPP;
+
hash = sock_hash_bucket_hash(key, key_size);
bucket = sock_hash_select_bucket(htab, hash);
@@ -986,6 +991,7 @@ static int sock_hash_update_common(struct bpf_map *map, void *key,
struct sk_psock *psock;
int ret;
+ WARN_ON_ONCE(irqs_disabled());
WARN_ON_ONCE(!rcu_read_lock_held());
if (unlikely(flags > BPF_EXIST))
return -EINVAL;
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-25 13:49 ` Jakub Sitnicki
@ 2024-03-29 5:29 ` John Fastabend
0 siblings, 0 replies; 8+ messages in thread
From: John Fastabend @ 2024-03-29 5:29 UTC (permalink / raw)
To: Jakub Sitnicki, Alexei Starovoitov, Edward Adam Davis, John Fastabend
Cc: syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs
Jakub Sitnicki wrote:
> On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote:
>
> [...]
>
> > But we also need to cover sock_map_unref->sock_sock_map_del_link called
> > from sock_hash_delete_elem. It also grabs a spin lock.
>
> On second look, no need to disable interrupts in
> sock_map_unref->sock_sock_map_del_link. Call is enclosed in the critical
> section in sock_hash_delete_elem that has been updated.
>
> I have a question, though, why are we patching sock_hash_free? It
> doesn't get called unless there are no more existing users of the BPF
> map. So nothing can mutate it from interrupt context.
>
> [...]
Agree sock_hash_free should be only after all refs are dropped.
Edward, did you want to send a v2 for this? Also if you want fixing the
sockmap case as well would be useful. Also happy to finish up the patches
if you would rather not.
Thanks,
John
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] bpf, sockmap: fix deadlock in rcu_report_exp_cpu_mult
2024-03-26 22:15 ` Jakub Sitnicki
@ 2024-03-29 15:52 ` Shung-Hsi Yu
0 siblings, 0 replies; 8+ messages in thread
From: Shung-Hsi Yu @ 2024-03-29 15:52 UTC (permalink / raw)
To: Jakub Sitnicki
Cc: Alexei Starovoitov, Edward Adam Davis, John Fastabend,
syzbot+c4f4d25859c2e5859988, 42.hyeyoo, andrii, ast, bpf, daniel,
davem, edumazet, kafai, kpsingh, kuba, linux-kernel, namhyung,
netdev, pabeni, peterz, songliubraving, syzkaller-bugs, yhs,
Xin Liu
On Tue, Mar 26, 2024 at 11:15:47PM +0100, Jakub Sitnicki wrote:
> On Mon, Mar 25, 2024 at 01:23 PM +01, Jakub Sitnicki wrote:
> > On Sat, Mar 23, 2024 at 12:08 AM -07, Alexei Starovoitov wrote:
> >> It seems this bug was causing multiple syzbot reports.
> > Any chance we could disallow mutating sockhash from interrupt context?
>
> I've been playing with the repro from one of the other reports:
>
> https://lore.kernel.org/all/CABOYnLzaRiZ+M1v7dPaeObnj_=S4JYmWbgrXaYsyBbWh=553vQ@mail.gmail.com/
Possibly also related:
- "A potential deadlock in sockhash map"[1] report awhile back
- commit ed17aa92dc56b ("bpf, sockmap: fix deadlocks in the sockhash and
sockmap")
- commit 8c5c2a4898e3d ("bpf, sockmap: Revert buggy deadlock fix in the
sockhash and sockmap")
1: https://lore.kernel.org/all/CABcoxUayum5oOqFMMqAeWuS8+EzojquSOSyDA3J_2omY=2EeAg@mail.gmail.com/
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2024-03-29 15:52 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2024-03-18 10:07 [syzbot] [bpf?] [net?] possible deadlock in rcu_report_exp_cpu_mult syzbot
2024-03-23 5:42 ` [PATCH] bpf, sockmap: fix " Edward Adam Davis
2024-03-23 7:08 ` Alexei Starovoitov
2024-03-25 12:23 ` Jakub Sitnicki
2024-03-25 13:49 ` Jakub Sitnicki
2024-03-29 5:29 ` John Fastabend
2024-03-26 22:15 ` Jakub Sitnicki
2024-03-29 15:52 ` Shung-Hsi Yu
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