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().

v1->v2:
  - add the missing Fixes tags per Eric's request.

Fixes: 0762216 ("tipc: fix uninit-value in tipc_nl_compat_bearer_enable")
Fixes: 8b66fee ("tipc: fix uninit-value in tipc_nl_compat_link_reset_stats")
Reported-by: [email protected]
Signed-off-by: Xin Long <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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;