[PATCH 5.15 054/139] bpf: Add schedule points in batch ops

Greg Kroah-Hartman
2022-02-28T17:54:08Z

From: Eric Dumazet <edumazet@google.com>

commit 75134f16e7dd0007aa474b281935c5f42e79f2c8 upstream.

syzbot reported various soft lockups caused by bpf batch operations.

INFO: task kworker/1:1:27 blocked for more than 140 seconds.
INFO: task hung in rcu_barrier

Nothing prevents batch ops to process huge amount of data,
we need to add schedule points in them.

Note that maybe_wait_bpf_programs(map) calls from
generic_map_delete_batch() can be factorized by moving
the call after the loop.

This will be done later in -next tree once we get this fix merged,
unless there is strong opinion doing this optimization sooner.

Fixes: aa2e93b8e58e ("bpf: Add generic support for update and delete batch ops")
Fixes: cb4d03ab499d ("bpf: Add generic support for lookup batch op")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Brian Vazquez <brianvv@google.com>
Link: https://lore.kernel.org/bpf/20220217181902.808742-1-eric.dumazet@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/bpf/syscall.c | 3 +++
1 file changed, 3 insertions(+)

--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1337,6 +1337,7 @@ int generic_map_delete_batch(struct bpf_
maybe_wait_bpf_programs(map);
if (err)
break;
+ cond_resched();
}
if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp)))
err = -EFAULT;
@@ -1394,6 +1395,7 @@ int generic_map_update_batch(struct bpf_

if (err)
break;
+ cond_resched();
}

if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp)))
@@ -1491,6 +1493,7 @@ int generic_map_lookup_batch(struct bpf_
swap(prev_key, key);
retry = MAP_LOOKUP_RETRIES;
cp++;
+ cond_resched();
}

if (err == -EFAULT)