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authorEric W. Biederman <ebiederm@xmission.com>2017-11-15 22:17:48 -0600
committerDavid S. Miller <davem@davemloft.net>2017-11-16 23:00:30 +0900
commit7c8a61d9ee1df0fb4747879fa67a99614eb62fec (patch)
treefc227e1dc13715dc2c9394d3af93de4eb979acf7 /net/sctp
parentcc54c1d32e6a4bb3f116721abf900513173e4d02 (diff)
net/sctp: Always set scope_id in sctp_inet6_skb_msgname
Alexandar Potapenko while testing the kernel with KMSAN and syzkaller discovered that in some configurations sctp would leak 4 bytes of kernel stack. Working with his reproducer I discovered that those 4 bytes that are leaked is the scope id of an ipv6 address returned by recvmsg. With a little code inspection and a shrewd guess I discovered that sctp_inet6_skb_msgname only initializes the scope_id field for link local ipv6 addresses to the interface index the link local address pertains to instead of initializing the scope_id field for all ipv6 addresses. That is almost reasonable as scope_id's are meaniningful only for link local addresses. Set the scope_id in all other cases to 0 which is not a valid interface index to make it clear there is nothing useful in the scope_id field. There should be no danger of breaking userspace as the stack leak guaranteed that previously meaningless random data was being returned. Fixes: 372f525b495c ("SCTP: Resync with LKSCTP tree.") History-tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reported-by: Alexander Potapenko <glider@google.com> Tested-by: Alexander Potapenko <glider@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
-rw-r--r--net/sctp/ipv6.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index a6dfa86c0201..3b18085e3b10 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -807,9 +807,10 @@ static void sctp_inet6_skb_msgname(struct sk_buff *skb, char *msgname,
addr->v6.sin6_flowinfo = 0;
addr->v6.sin6_port = sh->source;
addr->v6.sin6_addr = ipv6_hdr(skb)->saddr;
- if (ipv6_addr_type(&addr->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) {
+ if (ipv6_addr_type(&addr->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL)
addr->v6.sin6_scope_id = sctp_v6_skb_iif(skb);
- }
+ else
+ addr->v6.sin6_scope_id = 0;
}
*addr_len = sctp_v6_addr_to_user(sctp_sk(skb->sk), addr);