From 4a87a0ae8bc4a186842fb5f57454412de56f52bc Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Thu, 13 Aug 2020 14:10:58 -0400
Subject: [PATCH] fix a bug in the out-of-memory handling code in exec

---
 kernel/exec.c | 7 ++++---
 kernel/vm.c   | 3 +--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/exec.c b/kernel/exec.c
index 1077ac0..8a2d1dc 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -14,7 +14,7 @@ exec(char *path, char **argv)
 {
   char *s, *last;
   int i, off;
-  uint64 argc, sz, sp, ustack[MAXARG+1], stackbase;
+  uint64 argc, sz = 0, sp, ustack[MAXARG+1], stackbase;
   struct elfhdr elf;
   struct inode *ip;
   struct proghdr ph;
@@ -39,7 +39,6 @@ exec(char *path, char **argv)
     goto bad;
 
   // Load program into memory.
-  sz = 0;
   for(i=0, off=elf.phoff; i<elf.phnum; i++, off+=sizeof(ph)){
     if(readi(ip, 0, (uint64)&ph, off, sizeof(ph)) != sizeof(ph))
       goto bad;
@@ -49,8 +48,10 @@ exec(char *path, char **argv)
       goto bad;
     if(ph.vaddr + ph.memsz < ph.vaddr)
       goto bad;
-    if((sz = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz)) == 0)
+    uint64 sz1;
+    if((sz1 = uvmalloc(pagetable, sz, ph.vaddr + ph.memsz)) == 0)
       goto bad;
+    sz = sz1;
     if(ph.vaddr % PGSIZE != 0)
       goto bad;
     if(loadseg(pagetable, ph.vaddr, ip, ph.off, ph.filesz) < 0)
diff --git a/kernel/vm.c b/kernel/vm.c
index 2f3789f..bccb405 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -235,8 +235,7 @@ uvmalloc(pagetable_t pagetable, uint64 oldsz, uint64 newsz)
     return oldsz;
 
   oldsz = PGROUNDUP(oldsz);
-  a = oldsz;
-  for(; a < newsz; a += PGSIZE){
+  for(a = oldsz; a < newsz; a += PGSIZE){
     mem = kalloc();
     if(mem == 0){
       uvmdealloc(pagetable, a, oldsz);