Re: [PATCH net-next 1/9] bpf: prevent kprobe+bpf deadlocks

From: Daniel Borkmann
Date: Mon Mar 07 2016 - 05:08:09 EST


On 03/07/2016 02:58 AM, Alexei Starovoitov wrote:
if kprobe is placed within update or delete hash map helpers
that hold bucket spin lock and triggered bpf program is trying to
grab the spinlock for the same bucket on the same cpu, it will
deadlock.
Fix it by extending existing recursion prevention mechanism.

Note, map_lookup and other tracing helpers don't have this problem,
since they don't hold any locks and don't modify global data.
bpf_trace_printk has its own recursive check and ok as well.

Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>

LGTM

Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>