[PATCH 14/32] af_unix: Use mem_to_flex_dup() with struct unix_address

Kees Cook
2022-05-04T01:49:20Z

As part of the work to perform bounds checking on all memcpy() uses,
replace the open-coded a deserialization of bytes out of memory into a
trailing flexible array by using a flex_array.h helper to perform the
allocation, bounds checking, and copying.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Cong Wang <cong.wang@bytedance.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: netdev@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
include/net/af_unix.h | 14 ++++++++++++--
net/unix/af_unix.c | 7 ++-----
2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index a7ef624ed726..422535b71295 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -25,8 +25,18 @@ extern struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE];

struct unix_address {
refcount_t refcnt;
- int len;
- struct sockaddr_un name[];
+ DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(int, len);
+ union {
+ DECLARE_FLEX_ARRAY(struct sockaddr_un, name);
+ /*
+ * While a struct is used to access the flexible
+ * array, it may only be partially populated, and
+ * "len" above is actually tracking bytes, not a
+ * count of struct sockaddr_un elements, so also
+ * include a byte-size flexible array.
+ */
+ DECLARE_FLEX_ARRAY_ELEMENTS(u8, bytes);
+ };
};

struct unix_skb_parms {
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index e1dd9e9c8452..8410cbc82ded 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -244,15 +244,12 @@ EXPORT_SYMBOL_GPL(unix_peer_get);
static struct unix_address *unix_create_addr(struct sockaddr_un *sunaddr,
int addr_len)
{
- struct unix_address *addr;
+ struct unix_address *addr = NULL;

- addr = kmalloc(sizeof(*addr) + addr_len, GFP_KERNEL);
- if (!addr)
+ if (mem_to_flex_dup(&addr, sunaddr, addr_len, GFP_KERNEL))
return NULL;

refcount_set(&addr->refcnt, 1);
- addr->len = addr_len;
- memcpy(addr->name, sunaddr, addr_len);

return addr;
}
--
2.32.0