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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: daniel@iogearbox.net, ast@fb.com
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
	bpf@vger.kernel.org, netdev@vger.kernel.org,
	"Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Xiumei Mu" <xmu@redhat.com>
Subject: [PATCH bpf v2] cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled
Date: Thu, 16 Apr 2020 10:31:20 +0200	[thread overview]
Message-ID: <20200416083120.453718-1-toke@redhat.com> (raw)

When the kernel is built with CONFIG_DEBUG_PER_CPU_MAPS, the cpumap code
can trigger a spurious warning if CONFIG_CPUMASK_OFFSTACK is also set. This
happens because in this configuration, NR_CPUS can be larger than
nr_cpumask_bits, so the initial check in cpu_map_alloc() is not sufficient
to guard against hitting the warning in cpumask_check().

Fix this by explicitly checking the supplied key against the
nr_cpumask_bits variable before calling cpu_possible().

Fixes: 6710e1126934 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP")
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Reported-by: Xiumei Mu <xmu@redhat.com>
Tested-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
---
v2:
  - Move check to cpu_map_update_elem() to not affect max size of map

 kernel/bpf/cpumap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 70f71b154fa5..3fe0b006d2d2 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -469,7 +469,7 @@ static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
 		return -EOVERFLOW;
 
 	/* Make sure CPU is a valid possible cpu */
-	if (!cpu_possible(key_cpu))
+	if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
 		return -ENODEV;
 
 	if (qsize == 0) {
-- 
2.26.0


             reply	other threads:[~2020-04-16  8:33 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-16  8:31 Toke Høiland-Jørgensen [this message]
2020-04-16  8:43 ` [PATCH bpf v2] cpumap: Avoid warning when CONFIG_DEBUG_PER_CPU_MAPS is enabled Jesper Dangaard Brouer
2020-04-16 21:45   ` Song Liu
2020-04-21  1:40 ` Alexei Starovoitov

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