[PATCH 4.19 030/170] sctp: initialize sin6_flowinfo for ipv6 addrs in sctp_inet6addr_event

From: Greg Kroah-Hartman
Date: Mon Jan 07 2019 - 07:46:56 EST

4.19-stable review patch. If anyone has any objections, please let me know.


From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit 4a2eb0c37b4759416996fbb4c45b932500cf06d3 ]

syzbot reported a kernel-infoleak, which is caused by an uninitialized
field(sin6_flowinfo) of addr->a.v6 in sctp_inet6addr_event().
The call trace is as below:

BUG: KMSAN: kernel-infoleak in _copy_to_user+0x19a/0x230 lib/usercopy.c:33
CPU: 1 PID: 8164 Comm: syz-executor2 Not tainted 4.20.0-rc3+ #95
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x32d/0x480 lib/dump_stack.c:113
kmsan_report+0x12c/0x290 mm/kmsan/kmsan.c:683
kmsan_internal_check_memory+0x32a/0xa50 mm/kmsan/kmsan.c:743
kmsan_copy_to_user+0x78/0xd0 mm/kmsan/kmsan_hooks.c:634
_copy_to_user+0x19a/0x230 lib/usercopy.c:33
copy_to_user include/linux/uaccess.h:183 [inline]
sctp_getsockopt_local_addrs net/sctp/socket.c:5998 [inline]
sctp_getsockopt+0x15248/0x186f0 net/sctp/socket.c:7477
sock_common_getsockopt+0x13f/0x180 net/core/sock.c:2937
__sys_getsockopt+0x489/0x550 net/socket.c:1939
__do_sys_getsockopt net/socket.c:1950 [inline]
__se_sys_getsockopt+0xe1/0x100 net/socket.c:1947
__x64_sys_getsockopt+0x62/0x80 net/socket.c:1947
do_syscall_64+0xcf/0x110 arch/x86/entry/common.c:291

sin6_flowinfo is not really used by SCTP, so it will be fixed by simply
setting it to 0.

The issue exists since very beginning.
Thanks Alexander for the reproducer provided.

Reported-by: syzbot+ad5d327e6936a2e284be@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/sctp/ipv6.c | 1 +
1 file changed, 1 insertion(+)

--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -101,6 +101,7 @@ static int sctp_inet6addr_event(struct n
if (addr) {
addr->a.v6.sin6_family = AF_INET6;
addr->a.v6.sin6_port = 0;
+ addr->a.v6.sin6_flowinfo = 0;
addr->a.v6.sin6_addr = ifa->addr;
addr->a.v6.sin6_scope_id = ifa->idev->dev->ifindex;
addr->valid = 1;