CVE-2021-20255 patch adapted from QEMU patch by Stefan Weil

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1930646

Signed-off-by: Neha Agarwal <nehaagarwal@microsoft.com>
---
diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
index 16e95ef9cc..2474cf3dc2 100644
--- a/hw/net/eepro100.c
+++ b/hw/net/eepro100.c
@@ -279,6 +279,9 @@ typedef struct {
     /* Quasi static device properties (no need to save them). */
     uint16_t stats_size;
     bool has_extended_tcb_support;
+
+    /* Flag to avoid recursions. */
+    bool busy;
 } EEPRO100State;

 /* Word indices in EEPROM. */
@@ -837,6 +840,14 @@ static void action_command(EEPRO100State *s)
        Therefore we limit the number of iterations. */
     unsigned max_loop_count = 16;

+    if (s->busy) {
+        /* Prevent recursions. */
+        logout("recursion in %s:%u\n", __FILE__, __LINE__);
+        return;
+    }
+
+    s->busy = true;
+
     for (;;) {
         bool bit_el;
         bool bit_s;
@@ -933,6 +944,7 @@ static void action_command(EEPRO100State *s)
     }
     TRACE(OTHER, logout("CU list empty\n"));
     /* List is empty. Now CU is idle or suspended. */
+    s->busy = false;
 }

 static void eepro100_cu_command(EEPRO100State * s, uint8_t val)