linux-kernel - [PATCH 5.16 0233/1039] bpf: Disallow BPF_LOG_KERNEL log level for bpf(BPF_BTF

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Date:   Mon, 24 Jan 2022 19:33:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hou Tao <houtao1@...wei.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.16 0233/1039] bpf: Disallow BPF_LOG_KERNEL log level for bpf(BPF_BTF_LOAD)

From: Hou Tao <houtao1@...wei.com>

[ Upstream commit 866de407444398bc8140ea70de1dba5f91cc34ac ]

BPF_LOG_KERNEL is only used internally, so disallow bpf_btf_load()
to set log level as BPF_LOG_KERNEL. The same checking has already
been done in bpf_check(), so factor out a helper to check the
validity of log attributes and use it in both places.

Fixes: 8580ac9404f6 ("bpf: Process in-kernel BTF")
Signed-off-by: Hou Tao <houtao1@...wei.com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Yonghong Song <yhs@...com>
Acked-by: Martin KaFai Lau <kafai@...com>
Link: https://lore.kernel.org/bpf/20211203053001.740945-1-houtao1@huawei.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/bpf_verifier.h | 7 +++++++
 kernel/bpf/btf.c             | 3 +--
 kernel/bpf/verifier.c        | 6 +++---
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index c8a78e830fcab..182b16a910849 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -396,6 +396,13 @@ static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
 		 log->level == BPF_LOG_KERNEL);
 }
 
+static inline bool
+bpf_verifier_log_attr_valid(const struct bpf_verifier_log *log)
+{
+	return log->len_total >= 128 && log->len_total <= UINT_MAX >> 2 &&
+	       log->level && log->ubuf && !(log->level & ~BPF_LOG_MASK);
+}
+
 #define BPF_MAX_SUBPROGS 256
 
 struct bpf_subprog_info {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0cb1ceb91ca96..5e037070cb656 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4460,8 +4460,7 @@ static struct btf *btf_parse(bpfptr_t btf_data, u32 btf_data_size,
 		log->len_total = log_size;
 
 		/* log attributes have to be sane */
-		if (log->len_total < 128 || log->len_total > UINT_MAX >> 2 ||
-		    !log->level || !log->ubuf) {
+		if (!bpf_verifier_log_attr_valid(log)) {
 			err = -EINVAL;
 			goto errout;
 		}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4e51bf3f9603a..8ebabae31a431 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13960,11 +13960,11 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr)
 		log->ubuf = (char __user *) (unsigned long) attr->log_buf;
 		log->len_total = attr->log_size;
 
-		ret = -EINVAL;
 		/* log attributes have to be sane */
-		if (log->len_total < 128 || log->len_total > UINT_MAX >> 2 ||
-		    !log->level || !log->ubuf || log->level & ~BPF_LOG_MASK)
+		if (!bpf_verifier_log_attr_valid(log)) {
+			ret = -EINVAL;
 			goto err_unlock;
+		}
 	}
 
 	if (IS_ERR(btf_vmlinux)) {
-- 
2.34.1