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Date: Fri, 9 Mar 2018 16:19:11 -0800 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, "ast@...nel.org, daniel@...earbox.net, stable@...r.kernel.org, Eric Dumazet" <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com>, Daniel Borkmann <daniel@...earbox.net>, Eric Dumazet <edumazet@...gle.com> Subject: [PATCH 4.14 6/9] bpf: add schedule points in percpu arrays management 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet <edumazet@...gle.com> [ upstream commit 32fff239de37ef226d5b66329dd133f64d63b22d ] syszbot managed to trigger RCU detected stalls in bpf_array_free_percpu() It takes time to allocate a huge percpu map, but even more time to free it. Since we run in process context, use cond_resched() to yield cpu if needed. Fixes: a10423b87a7e ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Signed-off-by: Eric Dumazet <edumazet@...gle.com> Reported-by: syzbot <syzkaller@...glegroups.com> Signed-off-by: Daniel Borkmann <daniel@...earbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- kernel/bpf/arraymap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -23,8 +23,10 @@ static void bpf_array_free_percpu(struct { int i; - for (i = 0; i < array->map.max_entries; i++) + for (i = 0; i < array->map.max_entries; i++) { free_percpu(array->pptrs[i]); + cond_resched(); + } } static int bpf_array_alloc_percpu(struct bpf_array *array) @@ -40,6 +42,7 @@ static int bpf_array_alloc_percpu(struct return -ENOMEM; } array->pptrs[i] = ptr; + cond_resched(); } return 0;
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