diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-11-15 22:17:48 -0600 |
|---|---|---|
| committer | Moyster <oysterized@gmail.com> | 2019-05-02 16:59:52 +0200 |
| commit | 154dfe76fe2697d105b8ce13964de26f5b993551 (patch) | |
| tree | 31d0fb9523432f4c6a8d6ec8251f0f90112b4fd4 | |
| parent | 73b6968927a070042578b9a2803527739533f844 (diff) | |
net/sctp: Always set scope_id in sctp_inet6_skb_msgname
commit 7c8a61d9ee1df0fb4747879fa67a99614eb62fec upstream.
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.")
Change-Id: I24fe3eb3a92fb0435dc162ef62ed3a5b44b612c3
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>
[bwh: Backported to 3.16:
- Adjust context
- Add braces]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -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 206a755dc..9c22a633b 100644 --- a/net/sctp/ipv6.c +++ b/net/sctp/ipv6.c @@ -794,6 +794,8 @@ static void sctp_inet6_skb_msgname(struct sk_buff *skb, char *msgname, if (ipv6_addr_type(&sin6->sin6_addr) & IPV6_ADDR_LINKLOCAL) { struct sctp_ulpevent *ev = sctp_skb2event(skb); sin6->sin6_scope_id = ev->iif; + } else { + sin6->sin6_scope_id = 0; } } } |