From: Wander Lairson Costa wander.lairson@gmail.com

mainline inclusion from mainline-v6.12-rc4 commit 8b62645b09f870d70c7910e7550289d444239a46 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB3I26 CVE: CVE-2024-50138

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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 Conflicts: kernel/bpf/ringbuf.c [The conflicts were due to not merge the commits 457f44363a889] Signed-off-by: Xiaomeng Zhang zhangxiaomeng13@huawei.com --- 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 d21d4ba2eb39..984f4772a01e 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -36,7 +36,7 @@ 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; /* Consumer and producer counters are put into separate pages to allow * mapping consumer page as r/w, but restrict producer page to r/o. * This protects producer position from being modified by user-space @@ -139,7 +139,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) if (!rb) return ERR_PTR(-ENOMEM);

- spin_lock_init(&rb->spinlock); + raw_spin_lock_init(&rb->spinlock); init_waitqueue_head(&rb->waitq); init_irq_work(&rb->work, bpf_ringbuf_notify);

@@ -339,10 +339,10 @@ 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; @@ -368,7 +368,7 @@ 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; }

@@ -380,7 +380,7 @@ 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; }