[PATCH 3.2 070/140] af_key: fix buffer overread in verify_address_len()

Ben Hutchings
2018-02-28T17:23:53Z

From: Eric Biggers <ebiggers@google.com>

commit 06b335cb51af018d5feeff5dd4fd53847ddb675a upstream.

If a message sent to a PF_KEY socket ended with one of the extensions
that takes a 'struct sadb_address' but there were not enough bytes
remaining in the message for the ->sa_family member of the 'struct
sockaddr' which is supposed to follow, then verify_address_len() read
past the end of the message, into uninitialized memory. Fix it by
returning -EINVAL in this case.

This bug was found using syzkaller with KMSAN.

Reproducer:

#include <linux/pfkeyv2.h>
#include <sys/socket.h>
#include <unistd.h>

int main()
{
int sock = socket(PF_KEY, SOCK_RAW, PF_KEY_V2);
char buf[24] = { 0 };
struct sadb_msg *msg = (void *)buf;
struct sadb_address *addr = (void *)(msg + 1);

msg->sadb_msg_version = PF_KEY_V2;
msg->sadb_msg_type = SADB_DELETE;
msg->sadb_msg_len = 3;
addr->sadb_address_len = 1;
addr->sadb_address_exttype = SADB_EXT_ADDRESS_SRC;

write(sock, buf, 24);
}

Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/key/af_key.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -398,6 +398,11 @@ static int verify_address_len(const void
#endif
int len;

+ if (sp->sadb_address_len <
+ DIV_ROUND_UP(sizeof(*sp) + offsetofend(typeof(*addr), sa_family),
+ sizeof(uint64_t)))
+ return -EINVAL;
+
switch (addr->sa_family) {
case AF_INET:
len = DIV_ROUND_UP(sizeof(*sp) + sizeof(*sin), sizeof(uint64_t));