From: Florian Westphal <fw@xxxxxxxxx>
We have targets and standard targets -- the latter carries a verdict.
The ip/ip6tables validation functions will access t->verdict for the
standard targets to fetch the jump offset or verdict for chainloop
detection, but this happens before the targets get checked/validated.
Thus we also need to check for verdict presence here, else t->verdict
can point right after a blob.
Spotted with UBSAN while testing malformed blobs.
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/netfilter/x_tables.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index fa206ce..1cb7a27 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -540,6 +540,13 @@ int xt_compat_match_to_user(const struct xt_entry_match *m,
}
EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
+/* non-compat version may have padding after verdict */
+struct compat_xt_standard_target {
+ struct compat_xt_entry_target t;
+ compat_uint_t verdict;
+};
+
+/* see xt_check_entry_offsets */
int xt_compat_check_entry_offsets(const void *base,
unsigned int target_offset,
unsigned int next_offset)
@@ -557,6 +564,10 @@ int xt_compat_check_entry_offsets(const void *base,
if (target_offset + t->u.target_size > next_offset)
return -EINVAL;
+ if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
+ target_offset + sizeof(struct compat_xt_standard_target) != next_offset)
+ return -EINVAL;
+
return 0;
}
EXPORT_SYMBOL(xt_compat_check_entry_offsets);
@@ -596,6 +607,10 @@ int xt_check_entry_offsets(const void *base,
if (target_offset + t->u.target_size > next_offset)
return -EINVAL;
+ if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0 &&
+ target_offset + sizeof(struct xt_standard_target) != next_offset)
+ return -EINVAL;
+
return 0;
}
EXPORT_SYMBOL(xt_check_entry_offsets);
--
2.1.4
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
