rxrpc: out of bound read in debug code

Smatch complains because we are using an untrusted index into the
rxrpc_acks[] array.  It's just a read and it's only in the debug code,
but it's simple enough to add a check and fix it.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 7 deletions

diff --git a/net/rxrpc/ar-ack.c b/net/rxrpc/ar-ack.c
index e4d9cbcff402..cd97a0ce48d8 100644
--- a/net/rxrpc/ar-ack.c
+++ b/net/rxrpc/ar-ack.c
@@ -21,10 +21,17 @@
 
 static unsigned int rxrpc_ack_defer = 1;
 
-static const char *const rxrpc_acks[] = {
-        "---", "REQ", "DUP", "OOS", "WIN", "MEM", "PNG", "PNR", "DLY", "IDL",
-        "-?-"
-};
+static const char *rxrpc_acks(u8 reason)
+{
+        static const char *const str[] = {
+                "---", "REQ", "DUP", "OOS", "WIN", "MEM", "PNG", "PNR", "DLY",
+                "IDL", "-?-"
+        };
+
+        if (reason >= ARRAY_SIZE(str))
+                reason = ARRAY_SIZE(str) - 1;
+        return str[reason];
+}
 
 static const s8 rxrpc_ack_priority[] = {
         [0]                             = 0,
@@ -50,7 +57,7 @@ void __rxrpc_propose_ACK(struct rxrpc_call *call, u8 ack_reason,
         ASSERTCMP(prior, >, 0);
 
         _enter("{%d},%s,%%%x,%u",
-               call->debug_id, rxrpc_acks[ack_reason], ntohl(serial),
+               call->debug_id, rxrpc_acks(ack_reason), ntohl(serial),
                immediate);
 
         if (prior < rxrpc_ack_priority[call->ackr_reason]) {
@@ -637,7 +644,7 @@ process_further:
                        hard,
                        ntohl(ack.previousPacket),
                        ntohl(ack.serial),
-                       rxrpc_acks[ack.reason],
+                       rxrpc_acks(ack.reason),
                        ack.nAcks);
 
                 rxrpc_extract_ackinfo(call, skb, latest, ack.nAcks);
@@ -1180,7 +1187,7 @@ send_ACK:
                ntohl(ack.firstPacket),
                ntohl(ack.previousPacket),
                ntohl(ack.serial),
-               rxrpc_acks[ack.reason],
+               rxrpc_acks(ack.reason),
                ack.nAcks);
 
         del_timer_sync(&call->ack_timer);