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| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-11-15 22:17:48 -0600 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-11-16 23:00:30 +0900 |
| commit | 7c8a61d9ee1df0fb4747879fa67a99614eb62fec (patch) | |
| tree | fc227e1dc13715dc2c9394d3af93de4eb979acf7 /net/sctp | |
| parent | cc54c1d32e6a4bb3f116721abf900513173e4d02 (diff) | |
| download | linux-7c8a61d9ee1df0fb4747879fa67a99614eb62fec.tar.gz linux-7c8a61d9ee1df0fb4747879fa67a99614eb62fec.tar.bz2 linux-7c8a61d9ee1df0fb4747879fa67a99614eb62fec.zip | |
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.c | 5 |
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); |