4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/arraymap.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -20,8 +20,10 @@ 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)
@@ -37,6 +39,7 @@ static int bpf_array_alloc_percpu(struct
return -ENOMEM;
}
array->pptrs[i] = ptr;
+ cond_resched();
}
return 0;