6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wander Lairson Costa <wander.lairson@xxxxxxxxx>
[ 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@xxxxxxxxxx>
Signed-off-by: Wander Lairson Costa <wander.lairson@xxxxxxxxx>
Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240920190700.617253-1-wander@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 a1911391a864c..af75c54eb84fb 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -37,7 +37,7 @@ 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
@@ -170,7 +170,7 @@ 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);
@@ -407,10 +407,10 @@ 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;
@@ -436,7 +436,7 @@ 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;
}
@@ -448,7 +448,7 @@ 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;
}
--
2.43.0
