5.4-stable review patch. If anyone has any objections, please let me know.
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From: Toke Høiland-Jørgensen toke@redhat.com
[ Upstream commit a34a9f1a19afe9c60ca0ea61dfeee63a1c2baac8 ]
Sysbot discovered that the queue and stack maps can deadlock if they are being used from a BPF program that can be called from NMI context (such as one that is attached to a perf HW counter event). To fix this, add an in_nmi() check and use raw_spin_trylock() in NMI context, erroring out if grabbing the lock fails.
Fixes: f1a2e44a3aec ("bpf: add queue and stack maps") Reported-by: Hsin-Wei Hung hsinweih@uci.edu Tested-by: Hsin-Wei Hung hsinweih@uci.edu Co-developed-by: Hsin-Wei Hung hsinweih@uci.edu Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com Link: https://lore.kernel.org/r/20230911132815.717240-1-toke@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/queue_stack_maps.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c index f697647ceb547..26ba7cb01136c 100644 --- a/kernel/bpf/queue_stack_maps.c +++ b/kernel/bpf/queue_stack_maps.c @@ -118,7 +118,12 @@ static int __queue_map_get(struct bpf_map *map, void *value, bool delete) int err = 0; void *ptr;
- raw_spin_lock_irqsave(&qs->lock, flags); + if (in_nmi()) { + if (!raw_spin_trylock_irqsave(&qs->lock, flags)) + return -EBUSY; + } else { + raw_spin_lock_irqsave(&qs->lock, flags); + }
if (queue_stack_map_is_empty(qs)) { memset(value, 0, qs->map.value_size); @@ -148,7 +153,12 @@ static int __stack_map_get(struct bpf_map *map, void *value, bool delete) void *ptr; u32 index;
- raw_spin_lock_irqsave(&qs->lock, flags); + if (in_nmi()) { + if (!raw_spin_trylock_irqsave(&qs->lock, flags)) + return -EBUSY; + } else { + raw_spin_lock_irqsave(&qs->lock, flags); + }
if (queue_stack_map_is_empty(qs)) { memset(value, 0, qs->map.value_size); @@ -213,7 +223,12 @@ static int queue_stack_map_push_elem(struct bpf_map *map, void *value, if (flags & BPF_NOEXIST || flags > BPF_EXIST) return -EINVAL;
- raw_spin_lock_irqsave(&qs->lock, irq_flags); + if (in_nmi()) { + if (!raw_spin_trylock_irqsave(&qs->lock, irq_flags)) + return -EBUSY; + } else { + raw_spin_lock_irqsave(&qs->lock, irq_flags); + }
if (queue_stack_map_is_full(qs)) { if (!replace) {