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Subject[PATCH 4.20 090/111] tipc: fix uninit-value in tipc_nl_compat_link_set
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ying Xue <ying.xue@windriver.com>

commit edf5ff04a45750ac8ce2435974f001dc9cfbf055 upstream.

syzbot reports following splat:

BUG: KMSAN: uninit-value in strlen+0x3b/0xa0 lib/string.c:486
CPU: 1 PID: 9306 Comm: syz-executor172 Not tainted 4.20.0-rc7+ #2
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+0x173/0x1d0 lib/dump_stack.c:113
kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:613
__msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313
strlen+0x3b/0xa0 lib/string.c:486
nla_put_string include/net/netlink.h:1154 [inline]
__tipc_nl_compat_link_set net/tipc/netlink_compat.c:708 [inline]
tipc_nl_compat_link_set+0x929/0x1220 net/tipc/netlink_compat.c:744
__tipc_nl_compat_doit net/tipc/netlink_compat.c:311 [inline]
tipc_nl_compat_doit+0x3aa/0xaf0 net/tipc/netlink_compat.c:344
tipc_nl_compat_handle net/tipc/netlink_compat.c:1107 [inline]
tipc_nl_compat_recv+0x14d7/0x2760 net/tipc/netlink_compat.c:1210
genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
netlink_rcv_skb+0x444/0x640 net/netlink/af_netlink.c:2477
genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
netlink_unicast+0xf40/0x1020 net/netlink/af_netlink.c:1336
netlink_sendmsg+0x127f/0x1300 net/netlink/af_netlink.c:1917
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg net/socket.c:631 [inline]
___sys_sendmsg+0xdb9/0x11b0 net/socket.c:2116
__sys_sendmsg net/socket.c:2154 [inline]
__do_sys_sendmsg net/socket.c:2163 [inline]
__se_sys_sendmsg+0x305/0x460 net/socket.c:2161
__x64_sys_sendmsg+0x4a/0x70 net/socket.c:2161
do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
entry_SYSCALL_64_after_hwframe+0x63/0xe7

The uninitialised access happened in
nla_put_string(skb, TIPC_NLA_LINK_NAME, lc->name)

This is because lc->name string is not validated before it's used.

Reported-by: syzbot+d78b8a29241a195aefb8@syzkaller.appspotmail.com
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/tipc/netlink_compat.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -762,9 +762,14 @@ static int tipc_nl_compat_link_set(struc
struct tipc_link_config *lc;
struct tipc_bearer *bearer;
struct tipc_media *media;
+ int len;

lc = (struct tipc_link_config *)TLV_DATA(msg->req);

+ len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+ if (!string_is_valid(lc->name, len))
+ return -EINVAL;
+
media = tipc_media_find(lc->name);
if (media) {
cmd->doit = &__tipc_nl_media_set;

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