6.11-stable review patch. If anyone has any objections, please let me know.
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From: Wander Lairson Costa wander.lairson@gmail.com
[ Upstream commit 8b62645b09f870d70c7910e7550289d444239a46 ]
The function __bpf_ringbuf_reserve is invoked from a tracepoint, which disables preemption. Using spinlock_t in this context can lead to a "sleep in atomic" warning in the RT variant. This issue is illustrated in the example below:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 556208, name: test_progs preempt_count: 1, expected: 0 RCU nest depth: 1, expected: 1 INFO: lockdep is turned off. Preemption disabled at: [<ffffd33a5c88ea44>] migrate_enable+0xc0/0x39c CPU: 7 PID: 556208 Comm: test_progs Tainted: G Hardware name: Qualcomm SA8775P Ride (DT) Call trace: dump_backtrace+0xac/0x130 show_stack+0x1c/0x30 dump_stack_lvl+0xac/0xe8 dump_stack+0x18/0x30 __might_resched+0x3bc/0x4fc rt_spin_lock+0x8c/0x1a4 __bpf_ringbuf_reserve+0xc4/0x254 bpf_ringbuf_reserve_dynptr+0x5c/0xdc bpf_prog_ac3d15160d62622a_test_read_write+0x104/0x238 trace_call_bpf+0x238/0x774 perf_call_bpf_enter.isra.0+0x104/0x194 perf_syscall_enter+0x2f8/0x510 trace_sys_enter+0x39c/0x564 syscall_trace_enter+0x220/0x3c0 do_el0_svc+0x138/0x1dc el0_svc+0x54/0x130 el0t_64_sync_handler+0x134/0x150 el0t_64_sync+0x17c/0x180
Switch the spinlock to raw_spinlock_t to avoid this error.
Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") Reported-by: Brian Grech bgrech@redhat.com Signed-off-by: Wander Lairson Costa wander.lairson@gmail.com Signed-off-by: Wander Lairson Costa wander@redhat.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/r/20240920190700.617253-1-wander@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/ringbuf.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index e20b90c361316..de3b681d1d13d 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -29,7 +29,7 @@ struct bpf_ringbuf { u64 mask; struct page **pages; int nr_pages; - spinlock_t spinlock ____cacheline_aligned_in_smp; + raw_spinlock_t spinlock ____cacheline_aligned_in_smp; /* For user-space producer ring buffers, an atomic_t busy bit is used * to synchronize access to the ring buffers in the kernel, rather than * the spinlock that is used for kernel-producer ring buffers. This is @@ -173,7 +173,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) if (!rb) return NULL;
- spin_lock_init(&rb->spinlock); + raw_spin_lock_init(&rb->spinlock); atomic_set(&rb->busy, 0); init_waitqueue_head(&rb->waitq); init_irq_work(&rb->work, bpf_ringbuf_notify); @@ -421,10 +421,10 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) cons_pos = smp_load_acquire(&rb->consumer_pos);
if (in_nmi()) { - if (!spin_trylock_irqsave(&rb->spinlock, flags)) + if (!raw_spin_trylock_irqsave(&rb->spinlock, flags)) return NULL; } else { - spin_lock_irqsave(&rb->spinlock, flags); + raw_spin_lock_irqsave(&rb->spinlock, flags); }
pend_pos = rb->pending_pos; @@ -450,7 +450,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) */ if (new_prod_pos - cons_pos > rb->mask || new_prod_pos - pend_pos > rb->mask) { - spin_unlock_irqrestore(&rb->spinlock, flags); + raw_spin_unlock_irqrestore(&rb->spinlock, flags); return NULL; }
@@ -462,7 +462,7 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) /* pairs with consumer's smp_load_acquire() */ smp_store_release(&rb->producer_pos, new_prod_pos);
- spin_unlock_irqrestore(&rb->spinlock, flags); + raw_spin_unlock_irqrestore(&rb->spinlock, flags);
return (void *)hdr + BPF_RINGBUF_HDR_SZ; }