Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in __bpf_ringbuf_reserve
============================================
WARNING: possible recursive locking detected
6.15.0-rc1-syzkaller-ge618ee89561b #0 Not tainted
--------------------------------------------
kworker/2:3/6044 is trying to acquire lock:
ffffc90006f360d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:423
but task is already holding lock:
ffffc900070410d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:423
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&rb->spinlock);
lock(&rb->spinlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
6 locks held by kworker/2:3/6044:
#0: ffff88801b48ad48 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
#1: ffffc90004c1fd18 ((work_completion)(&(&ssp->srcu_sup->work)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
#2: ffff88801ea8f158 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: srcu_advance_state kernel/rcu/srcutree.c:1701 [inline]
#2: ffff88801ea8f158 (&ssp->srcu_sup->srcu_gp_mutex){+.+.}-{4:4}, at: process_srcu+0x73/0x1920 kernel/rcu/srcutree.c:1861
#3: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#3: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#3: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2362 [inline]
#3: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1b6/0x590 kernel/trace/bpf_trace.c:2404
#4: ffffc900070410d8 (&rb->spinlock){-.-.}-{2:2}, at: __bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:423
#5: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#5: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
#5: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2362 [inline]
#5: ffffffff8e3c15c0 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1b6/0x590 kernel/trace/bpf_trace.c:2404
stack backtrace:
CPU: 2 UID: 0 PID: 6044 Comm: kworker/2:3 Not tainted 6.15.0-rc1-syzkaller-ge618ee89561b #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: rcu_gp process_srcu
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_deadlock_bug+0x1e9/0x240 kernel/locking/lockdep.c:3042
check_deadlock kernel/locking/lockdep.c:3094 [inline]
validate_chain kernel/locking/lockdep.c:3896 [inline]
__lock_acquire+0xff7/0x1ba0 kernel/locking/lockdep.c:5235
lock_acquire kernel/locking/lockdep.c:5866 [inline]
lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162
__bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:423
____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:474 [inline]
bpf_ringbuf_reserve+0x57/0x90 kernel/bpf/ringbuf.c:466
bpf_prog_385141c453c15099+0x36/0x5d
bpf_dispatcher_nop_func include/linux/bpf.h:1316 [inline]
__bpf_prog_run include/linux/filter.h:718 [inline]
bpf_prog_run include/linux/filter.h:725 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2363 [inline]
bpf_trace_run2+0x230/0x590 kernel/trace/bpf_trace.c:2404
__bpf_trace_contention_begin+0xc9/0x110 include/trace/events/lock.h:95
__traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
__preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
class_preempt_notrace_destructor include/linux/preempt.h:482 [inline]
__do_trace_contention_begin include/trace/events/lock.h:95 [inline]
trace_contention_begin.constprop.0+0xde/0x160 include/trace/events/lock.h:95
__pv_queued_spin_lock_slowpath+0x109/0xcf0 kernel/locking/qspinlock.c:219
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:572 [inline]
queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x20e/0x2b0 kernel/locking/spinlock_debug.c:116
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:111 [inline]
_raw_spin_lock_irqsave+0x42/0x60 kernel/locking/spinlock.c:162
__bpf_ringbuf_reserve+0x36e/0x4b0 kernel/bpf/ringbuf.c:423
____bpf_ringbuf_reserve kernel/bpf/ringbuf.c:474 [inline]
bpf_ringbuf_reserve+0x57/0x90 kernel/bpf/ringbuf.c:466
bpf_prog_385141c453c15099+0x36/0x5d
bpf_dispatcher_nop_func include/linux/bpf.h:1316 [inline]
__bpf_prog_run include/linux/filter.h:718 [inline]
bpf_prog_run include/linux/filter.h:725 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2363 [inline]
bpf_trace_run2+0x230/0x590 kernel/trace/bpf_trace.c:2404
__bpf_trace_contention_begin+0xc9/0x110 include/trace/events/lock.h:95
__traceiter_contention_begin+0x5a/0xa0 include/trace/events/lock.h:95
__do_trace_contention_begin include/trace/events/lock.h:95 [inline]
trace_contention_begin+0xc1/0x130 include/trace/events/lock.h:95
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x1a6/0xb90 kernel/locking/mutex.c:746
srcu_advance_state kernel/rcu/srcutree.c:1701 [inline]
process_srcu+0x73/0x1920 kernel/rcu/srcutree.c:1861
process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238
process_scheduled_works kernel/workqueue.c:3319 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400
kthread+0x3c2/0x780 kernel/kthread.c:464
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Tested on:
commit: e618ee89 Merge tag 'spi-fix-v6.15-rc1' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10461c04580000
kernel config: https://syzkaller.appspot.com/x/.config?x=36c5de4d99134dda
dashboard link: https://syzkaller.appspot.com/bug?extid=850aaf14624dc0c6d366
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
Note: no patches were applied.
