netdev - [PATCH net] tipc: check msg->req data len in tipc_nl_compat_bearer

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Date:   Mon, 24 Jun 2019 15:59:06 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, Jon Maloy <jon.maloy@...csson.com>,
        Ying Xue <ying.xue@...driver.com>,
        tipc-discussion@...ts.sourceforge.net,
        syzkaller-bugs@...glegroups.com
Subject: [PATCH net] tipc: check msg->req data len in tipc_nl_compat_bearer_disable

This patch is to fix an uninit-value issue, reported by syzbot:

  BUG: KMSAN: uninit-value in memchr+0xce/0x110 lib/string.c:981
  Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x191/0x1f0 lib/dump_stack.c:113
    kmsan_report+0x130/0x2a0 mm/kmsan/kmsan.c:622
    __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:310
    memchr+0xce/0x110 lib/string.c:981
    string_is_valid net/tipc/netlink_compat.c:176 [inline]
    tipc_nl_compat_bearer_disable+0x2a1/0x480 net/tipc/netlink_compat.c:449
    __tipc_nl_compat_doit net/tipc/netlink_compat.c:327 [inline]
    tipc_nl_compat_doit+0x3ac/0xb00 net/tipc/netlink_compat.c:360
    tipc_nl_compat_handle net/tipc/netlink_compat.c:1178 [inline]
    tipc_nl_compat_recv+0x1b1b/0x27b0 net/tipc/netlink_compat.c:1281

TLV_GET_DATA_LEN() may return a negtive int value, which will be
used as size_t (becoming a big unsigned long) passed into memchr,
cause this issue.

Similar to what it does in tipc_nl_compat_bearer_enable(), this
fix is to return -EINVAL when TLV_GET_DATA_LEN() is negtive in
tipc_nl_compat_bearer_disable(), as well as in
tipc_nl_compat_link_stat_dump() and tipc_nl_compat_link_reset_stats().

Reported-by: syzbot+30eaa8bf392f7fafffaf@...kaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/tipc/netlink_compat.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index c6a04c0..cf15506 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -445,7 +445,11 @@ static int tipc_nl_compat_bearer_disable(struct tipc_nl_compat_cmd_doit *cmd,
 	if (!bearer)
 		return -EMSGSIZE;
 
-	len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_BEARER_NAME);
+	len = TLV_GET_DATA_LEN(msg->req);
+	if (len <= 0)
+		return -EINVAL;
+
+	len = min_t(int, len, TIPC_MAX_BEARER_NAME);
 	if (!string_is_valid(name, len))
 		return -EINVAL;
 
@@ -539,7 +543,11 @@ static int tipc_nl_compat_link_stat_dump(struct tipc_nl_compat_msg *msg,
 
 	name = (char *)TLV_DATA(msg->req);
 
-	len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+	len = TLV_GET_DATA_LEN(msg->req);
+	if (len <= 0)
+		return -EINVAL;
+
+	len = min_t(int, len, TIPC_MAX_BEARER_NAME);
 	if (!string_is_valid(name, len))
 		return -EINVAL;
 
@@ -817,7 +825,11 @@ static int tipc_nl_compat_link_reset_stats(struct tipc_nl_compat_cmd_doit *cmd,
 	if (!link)
 		return -EMSGSIZE;
 
-	len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_LINK_NAME);
+	len = TLV_GET_DATA_LEN(msg->req);
+	if (len <= 0)
+		return -EINVAL;
+
+	len = min_t(int, len, TIPC_MAX_BEARER_NAME);
 	if (!string_is_valid(name, len))
 		return -EINVAL;
 
-- 
2.1.0