[PATCH 5.4 24/43] net: sctp: Fix IPv6 ancestor_size calc in sctp_copy_descendant

Greg Kroah-Hartman
2020-09-25T12:52:01Z

From: Henry Ptasinski <hptasinski@google.com>

[ Upstream commit fe81d9f6182d1160e625894eecb3d7ff0222cac5 ]

When calculating ancestor_size with IPv6 enabled, simply using
sizeof(struct ipv6_pinfo) doesn't account for extra bytes needed for
alignment in the struct sctp6_sock. On x86, there aren't any extra
bytes, but on ARM the ipv6_pinfo structure is aligned on an 8-byte
boundary so there were 4 pad bytes that were omitted from the
ancestor_size calculation. This would lead to corruption of the
pd_lobby pointers, causing an oops when trying to free the sctp
structure on socket close.

Fixes: 636d25d557d1 ("sctp: not copy sctp_sock pd_lobby in sctp_copy_descendant")
Signed-off-by: Henry Ptasinski <hptasinski@google.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/sctp/structs.h | 8 +++++---
net/sctp/socket.c | 9 +++------
2 files changed, 8 insertions(+), 9 deletions(-)

--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -224,12 +224,14 @@ struct sctp_sock {
data_ready_signalled:1;

atomic_t pd_mode;
+
+ /* Fields after this point will be skipped on copies, like on accept
+ * and peeloff operations
+ */
+
/* Receive to here while partial delivery is in effect. */
struct sk_buff_head pd_lobby;

- /* These must be the last fields, as they will skipped on copies,
- * like on accept and peeloff operations
- */
struct list_head auto_asconf_list;
int do_auto_asconf;
};
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9337,13 +9337,10 @@ void sctp_copy_sock(struct sock *newsk,
static inline void sctp_copy_descendant(struct sock *sk_to,
const struct sock *sk_from)
{
- int ancestor_size = sizeof(struct inet_sock) +
- sizeof(struct sctp_sock) -
- offsetof(struct sctp_sock, pd_lobby);
-
- if (sk_from->sk_family == PF_INET6)
- ancestor_size += sizeof(struct ipv6_pinfo);
+ size_t ancestor_size = sizeof(struct inet_sock);

+ ancestor_size += sk_from->sk_prot->obj_size;
+ ancestor_size -= offsetof(struct sctp_sock, pd_lobby);
__inet_sk_copy_descendant(sk_to, sk_from, ancestor_size);
}