linux-kernel - [PATCH 5.2 04/20] bpf: fix NULL deref in btf_type_is_resolve_source

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Message-Id: <20190802092058.345293259@linuxfoundation.org>
Date:   Fri,  2 Aug 2019 11:39:58 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, syzbot <syzkaller@...glegroups.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH 5.2 04/20] bpf: fix NULL deref in btf_type_is_resolve_source_only

From: Stanislav Fomichev <sdf@...gle.com>

commit e4f07120210a1794c1f1ae64d209a2fbc7bd2682 upstream.

Commit 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
added invocations of btf_type_is_resolve_source_only before
btf_type_nosize_or_null which checks for the NULL pointer.
Swap the order of btf_type_nosize_or_null and
btf_type_is_resolve_source_only to make sure the do the NULL pointer
check first.

Fixes: 1dc92851849c ("bpf: kernel side support for BTF Var and DataSec")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
Acked-by: Andrii Nakryiko <andriin@...com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/bpf/btf.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -1928,8 +1928,8 @@ static int btf_array_resolve(struct btf_
 	/* Check array->index_type */
 	index_type_id = array->index_type;
 	index_type = btf_type_by_id(btf, index_type_id);
-	if (btf_type_is_resolve_source_only(index_type) ||
-	    btf_type_nosize_or_null(index_type)) {
+	if (btf_type_nosize_or_null(index_type) ||
+	    btf_type_is_resolve_source_only(index_type)) {
 		btf_verifier_log_type(env, v->t, "Invalid index");
 		return -EINVAL;
 	}
@@ -1948,8 +1948,8 @@ static int btf_array_resolve(struct btf_
 	/* Check array->type */
 	elem_type_id = array->type;
 	elem_type = btf_type_by_id(btf, elem_type_id);
-	if (btf_type_is_resolve_source_only(elem_type) ||
-	    btf_type_nosize_or_null(elem_type)) {
+	if (btf_type_nosize_or_null(elem_type) ||
+	    btf_type_is_resolve_source_only(elem_type)) {
 		btf_verifier_log_type(env, v->t,
 				      "Invalid elem");
 		return -EINVAL;
@@ -2170,8 +2170,8 @@ static int btf_struct_resolve(struct btf
 		const struct btf_type *member_type = btf_type_by_id(env->btf,
 								member_type_id);
 
-		if (btf_type_is_resolve_source_only(member_type) ||
-		    btf_type_nosize_or_null(member_type)) {
+		if (btf_type_nosize_or_null(member_type) ||
+		    btf_type_is_resolve_source_only(member_type)) {
 			btf_verifier_log_member(env, v->t, member,
 						"Invalid member");
 			return -EINVAL;