[PATCH 5.7 31/79] bpf: Fix NULL pointer dereference in __btf_resolve_helper_id()

Greg Kroah-Hartman
2020-08-10T15:41:22Z

From: Peilin Ye <yepeilin.cs@gmail.com>

[ Upstream commit 5b801dfb7feb2738975d80223efc2fc193e55573 ]

Prevent __btf_resolve_helper_id() from dereferencing `btf_vmlinux`
as NULL. This patch fixes the following syzbot bug:

https://syzkaller.appspot.com/bug?id=f823224ada908fa5c207902a5a62065e53ca0fcc

Reported-by: syzbot+ee09bda7017345f1fbe6@syzkaller.appspotmail.com
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200714180904.277512-1-yepeilin.cs@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/btf.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index d1f5d428c9fe2..6cafc596631c3 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4011,6 +4011,11 @@ static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
const char *tname, *sym;
u32 btf_id, i;

+ if (!btf_vmlinux) {
+ bpf_log(log, "btf_vmlinux doesn't exist\n");
+ return -EINVAL;
+ }
+
if (IS_ERR(btf_vmlinux)) {
bpf_log(log, "btf_vmlinux is malformed\n");
return -EINVAL;
--
2.25.1