[PATCH net] netlabel: out of bound access in cipso_v4_validate()

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

syzkaller found another out of bound access in ip_options_compile(),
or more exactly in cipso_v4_validate()

Fixes: 20e2a8648596 ("cipso: handle CIPSO options correctly when NetLabel is 
disabled")
Fixes: 446fda4f2682 ("[NetLabel]: CIPSOv4 engine")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: Dmitry Vyukov  <dvyu...@google.com>
Cc: Paul Moore <p...@paul-moore.com>
---
 include/net/cipso_ipv4.h |    4 ++++
 net/ipv4/cipso_ipv4.c    |    4 ++++
 2 files changed, 8 insertions(+)

diff --git a/include/net/cipso_ipv4.h b/include/net/cipso_ipv4.h
index 
3ebb168b9afc68ad639b5d32f6182a845c83d759..a34b141f125f0032662f147b598c9fef4fb4bcef
 100644
--- a/include/net/cipso_ipv4.h
+++ b/include/net/cipso_ipv4.h
@@ -309,6 +309,10 @@ static inline int cipso_v4_validate(const struct sk_buff 
*skb,
        }
 
        for (opt_iter = 6; opt_iter < opt_len;) {
+               if (opt_iter + 1 == opt_len) {
+                       err_offset = opt_iter;
+                       goto out;
+               }
                tag_len = opt[opt_iter + 1];
                if ((tag_len == 0) || (tag_len > (opt_len - opt_iter))) {
                        err_offset = opt_iter + 1;
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 
72d6f056d863603c959e1d04b9f863909a37c758..ae206163c273381ba6e8bd8a24fa050619a4a6ae
 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1587,6 +1587,10 @@ int cipso_v4_validate(const struct sk_buff *skb, 
unsigned char **option)
                                goto validate_return_locked;
                        }
 
+               if (opt_iter + 1 == opt_len) {
+                       err_offset = opt_iter;
+                       goto validate_return_locked;
+               }
                tag_len = tag[1];
                if (tag_len > (opt_len - opt_iter)) {
                        err_offset = opt_iter + 1;