diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-11-15 22:17:48 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-11-24 08:32:24 +0100 |
| commit | 51b8aea7abdeb522e5450c246912b6f4a491e1c8 (patch) | |
| tree | e593393e17896039d572ff28b087794dc41ec5d0 | |
| parent | ae93cefb94300fd67c48e68f08c943f2f1f363c8 (diff) | |
net/sctp: Always set scope_id in sctp_inet6_skb_msgname
[ Upstream commit 7c8a61d9ee1df0fb4747879fa67a99614eb62fec ]
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | net/sctp/ipv6.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c index e33e9bd4ed5a..8a61ccc37e12 100644 --- a/net/sctp/ipv6.c +++ b/net/sctp/ipv6.c @@ -806,6 +806,8 @@ static void sctp_inet6_skb_msgname(struct sk_buff *skb, char *msgname, if (ipv6_addr_type(&addr->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) { struct sctp_ulpevent *ev = sctp_skb2event(skb); addr->v6.sin6_scope_id = ev->iif; + } else { + addr->v6.sin6_scope_id = 0; } } |