From: Hou Tao <houtao@huaweicloud.com>
To: bpf@vger.kernel.org, Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andrii@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
KP Singh <kpsingh@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Lorenz Bauer <oss@lmb.io>,
houtao1@huawei.com
Subject: [PATCH bpf v2 6/9] bpf: Only allow sleepable program for resched-able iterator
Date: Wed, 10 Aug 2022 16:05:35 +0800 [thread overview]
Message-ID: <20220810080538.1845898-7-houtao@huaweicloud.com> (raw)
In-Reply-To: <20220810080538.1845898-1-houtao@huaweicloud.com>
From: Hou Tao <houtao1@huawei.com>
When a sleepable program is attached to a hash map iterator, might_fault()
will report "BUG: sleeping function called from invalid context..." if
CONFIG_DEBUG_ATOMIC_SLEEP is enabled. The reason is that rcu_read_lock()
is held in bpf_hash_map_seq_next() and won't be released until all elements
are traversed or bpf_hash_map_seq_stop() is called.
Fixing it by reusing BPF_ITER_RESCHED to indicate that only non-sleepable
program is allowed for iterator without BPF_ITER_RESCHED. We can revise
bpf_iter_link_attach() later if there are other conditions which may
cause rcu_read_lock() or spin_lock() issues.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
kernel/bpf/bpf_iter.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 4b112aa8bba3..97bb57493ed5 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -68,13 +68,18 @@ static void bpf_iter_done_stop(struct seq_file *seq)
iter_priv->done_stop = true;
}
+static inline bool bpf_iter_target_support_resched(const struct bpf_iter_target_info *tinfo)
+{
+ return tinfo->reg_info->feature & BPF_ITER_RESCHED;
+}
+
static bool bpf_iter_support_resched(struct seq_file *seq)
{
struct bpf_iter_priv_data *iter_priv;
iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
target_private);
- return iter_priv->tinfo->reg_info->feature & BPF_ITER_RESCHED;
+ return bpf_iter_target_support_resched(iter_priv->tinfo);
}
/* maximum visited objects before bailing out */
@@ -542,6 +547,10 @@ int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
if (!tinfo)
return -ENOENT;
+ /* Only allow sleepable program for resched-able iterator */
+ if (prog->aux->sleepable && !bpf_iter_target_support_resched(tinfo))
+ return -EINVAL;
+
link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
if (!link)
return -ENOMEM;
--
2.29.2
next prev parent reply other threads:[~2022-08-10 7:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-10 8:05 [PATCH bpf v2 0/9] fixes for bpf map iterator Hou Tao
2022-08-10 8:05 ` [PATCH bpf v2 1/9] bpf: Acquire map uref in .init_seq_private for array " Hou Tao
2022-08-10 8:05 ` [PATCH bpf v2 2/9] bpf: Acquire map uref in .init_seq_private for hash " Hou Tao
2022-08-10 8:05 ` [PATCH bpf v2 3/9] bpf: Acquire map uref in .init_seq_private for sock local storage " Hou Tao
2022-08-10 16:47 ` Martin KaFai Lau
2022-08-10 8:05 ` [PATCH bpf v2 4/9] bpf: Acquire map uref in .init_seq_private for sock{map,hash} iterator Hou Tao
2022-08-10 8:05 ` [PATCH bpf v2 5/9] bpf: Check the validity of max_rdwr_access for sock local storage map iterator Hou Tao
2022-08-10 16:59 ` Martin KaFai Lau
2022-08-10 8:05 ` Hou Tao [this message]
2022-08-10 8:05 ` [PATCH bpf v2 7/9] selftests/bpf: Add tests for reading a dangling map iter fd Hou Tao
2022-08-10 15:13 ` Yonghong Song
2022-08-10 8:05 ` [PATCH bpf v2 8/9] selftests/bpf: Add write tests for sk local storage map iterator Hou Tao
2022-08-10 17:05 ` Martin KaFai Lau
2022-08-10 8:05 ` [PATCH bpf v2 9/9] selftests/bpf: Ensure sleepable program is rejected by hash map iter Hou Tao
2022-08-10 17:20 ` [PATCH bpf v2 0/9] fixes for bpf map iterator patchwork-bot+netdevbpf
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