From 4babe183dae107fc249d4f853faa61b0653d8baa Mon Sep 17 00:00:00 2001
From: Stefan Rueger <stefan.rueger@urclocks.com>
Date: Sun, 24 Jul 2022 18:20:35 +0100
Subject: [PATCH] Initialise memory before avr_set_bits() calls in stk500.c and
 stk500v2.c

---
 src/stk500.c   |  5 ++---
 src/stk500v2.c | 11 +++++++++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/stk500.c b/src/stk500.c
index cb270036..fa013012 100644
--- a/src/stk500.c
+++ b/src/stk500.c
@@ -212,7 +212,6 @@ static int stk500_chip_erase(PROGRAMMER * pgm, AVRPART * p)
   pgm->pgm_led(pgm, ON);
 
   memset(cmd, 0, sizeof(cmd));
-
   avr_set_bits(p->op[AVR_OP_CHIP_ERASE], cmd);
   pgm->cmd(pgm, cmd, res);
   usleep(p->chip_erase_delay);
@@ -745,8 +744,8 @@ static int stk500_loadaddr(PROGRAMMER * pgm, AVRMEM * mem, unsigned int addr)
   if (lext != NULL) {
     ext_byte = (addr >> 16) & 0xff;
     if (ext_byte != PDATA(pgm)->ext_addr_byte) {
-      /* Either this is the first addr load, or a 64K word boundary is
-       * crossed, so set the ext addr byte */
+      /* Either this is the first addr load, or a different 64K word section */
+      memset(buf, 0, 4);
       avr_set_bits(lext, buf);
       avr_set_addr(lext, buf, addr);
       stk500_cmd(pgm, buf, buf);
diff --git a/src/stk500v2.c b/src/stk500v2.c
index 523d6539..b0ccaad2 100644
--- a/src/stk500v2.c
+++ b/src/stk500v2.c
@@ -991,6 +991,7 @@ static int stk500v2_chip_erase(PROGRAMMER * pgm, AVRPART * p)
   buf[0] = CMD_CHIP_ERASE_ISP;
   buf[1] = p->chip_erase_delay / 1000;
   buf[2] = 0;	// use delay (?)
+  memset(buf+3, 0, 4);
   avr_set_bits(p->op[AVR_OP_CHIP_ERASE], buf+3);
   result = stk500v2_command(pgm, buf, 7, sizeof(buf));
   usleep(p->chip_erase_delay);
@@ -1121,8 +1122,8 @@ retry:
   buf[5] = p->bytedelay;
   buf[6] = p->pollvalue;
   buf[7] = p->pollindex;
+  memset(buf+8, 0, 4);
   avr_set_bits(p->op[AVR_OP_PGM_ENABLE], buf+8);
-  buf[10] = buf[11] = 0;
 
   rv = stk500v2_command(pgm, buf, 12, sizeof(buf));
 
@@ -1957,12 +1958,12 @@ static int stk500isp_read_byte(PROGRAMMER * pgm, AVRPART * p, AVRMEM * mem,
     buf[0] = CMD_READ_SIGNATURE_ISP;
   }
 
-  memset(buf + 1, 0, 5);
   if ((op = mem->op[AVR_OP_READ]) == NULL) {
     avrdude_message(MSG_INFO, "%s: stk500isp_read_byte(): invalid operation AVR_OP_READ on %s memory\n",
                     progname, mem->desc);
     return -1;
   }
+  memset(buf+2, 0, 4);
   avr_set_bits(op, buf + 2);
   if ((pollidx = avr_get_output_index(op)) == -1) {
     avrdude_message(MSG_INFO, "%s: stk500isp_read_byte(): cannot determine pollidx to read %s memory\n",
@@ -2314,6 +2315,7 @@ static int stk500v2_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
               progname, p->desc);
       return -1;
     }
+    memset(cmds, 0, sizeof cmds);
     avr_set_bits(m->op[AVR_OP_LOADPAGE_LO], cmds);
     commandbuf[5] = cmds[0];
 
@@ -2322,6 +2324,8 @@ static int stk500v2_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
               progname, p->desc);
       return -1;
     }
+
+    memset(cmds, 0, sizeof cmds);
     avr_set_bits(m->op[AVR_OP_WRITEPAGE], cmds);
     commandbuf[6] = cmds[0];
 
@@ -2335,6 +2339,7 @@ static int stk500v2_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
               progname, p->desc);
       return -1;
     }
+    memset(cmds, 0, sizeof cmds);
     avr_set_bits(wop, cmds);
     commandbuf[5] = cmds[0];
     commandbuf[6] = 0;
@@ -2346,6 +2351,7 @@ static int stk500v2_paged_write(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
             progname, p->desc);
     return -1;
   }
+  memset(cmds, 0, sizeof cmds);
   avr_set_bits(rop, cmds);
   commandbuf[7] = cmds[0];
 
@@ -2549,6 +2555,7 @@ static int stk500v2_paged_load(PROGRAMMER * pgm, AVRPART * p, AVRMEM * m,
             progname, p->desc);
     return -1;
   }
+  memset(cmds, 0, sizeof cmds);
   avr_set_bits(rop, cmds);
   commandbuf[3] = cmds[0];