Fix buffer overflows and memory leaks caught by ASAN (#282)

The changes in this commit allow ksh to be built and run with
ASan[*], although for now it only works under vmalloc. Example
command to build ksh with ASan:
$ bin/package make CCFLAGS='-O0 -g -fsanitize=address'

[*] https://en.wikipedia.org/wiki/AddressSanitizer

src/cmd/INIT/mamake.c:
- Fix a few memory leaks in mamake. This doesn't fix all of the
  memory leaks ASan complains about (there is one remaining in the
  view() function), but it's enough to get ksh to build under ASan.

src/lib/libast/features/map.c,
src/lib/libast/misc/glob.c:
- Rename the ast globbing functions to _ast_glob() and
  _ast_globfree(). Without this change the globbing tests fail
  under ASan. See: https://github.com/att/ast/commit/2c49eb6e

src/cmd/ksh93/sh/{init,io,nvtree,subshell}.c:
- Fix buffer overflows by using strncmp(3) instead of memcmp(3).

src/cmd/ksh93/sh/name.c:
- Fix another invalid usage of memcmp by using strncmp instead.
  This change is also in one of Red Hat's patches:
  https://git.centos.org/rpms/ksh/blob/c8s/f/SOURCES/ksh-20120801-nv_open-memcmp.patch

Resolves: https://github.com/ksh93/ksh/issues/230

src/cmd/INIT/mamake.c

@@ -1079,13 +1079,23 @@ push(char* file, Stdio_t* fp, int flags)
 	else if (++state.sp >= &state.streams[elementsof(state.streams)])
 		report(3, "input stream stack overflow", NiL, (unsigned long)0);
 	if (state.sp->fp = fp)
-		state.sp->file = "pipeline";
+	{
+		if(state.sp->file)
+			free(state.sp->file);
+		state.sp->file = strdup("pipeline");
+		if(!state.sp->file)
+			report(3, "out of memory [push]", NiL, (unsigned long)0);
+	}
 	else if (flags & STREAM_PIPE)
 		report(3, "pipe error", file, (unsigned long)0);
 	else if (!file || !strcmp(file, "-") || !strcmp(file, "/dev/stdin"))
 	{
 		flags |= STREAM_KEEP;
-		state.sp->file = "/dev/stdin";
+		if(state.sp->file)
+			free(state.sp->file);
+		state.sp->file = strdup("/dev/stdin");
+		if(!state.sp->file)
+			report(3, "out of memory [push]", NiL, (unsigned long)0);
 		state.sp->fp = stdin;
 	}
 	else
@@ -1095,6 +1105,8 @@ push(char* file, Stdio_t* fp, int flags)
 		{
 			if (!(state.sp->fp = fopen(path, "r")))
 				report(3, "cannot read", path, (unsigned long)0);
+			if(state.sp->file)
+				free(state.sp->file);
 			state.sp->file = duplicate(path);
 			drop(buf);
 		}
@@ -1446,6 +1458,7 @@ require(char* lib, int dontcare)
 	Buf_t*		tmp;
 	struct stat	st;
 
+	int		tofree = 0;
 	static int	dynamic = -1;
 
 	if (dynamic < 0)
@@ -1490,7 +1503,10 @@ require(char* lib, int dontcare)
 			}
 		}
 		if (r != lib)
+		{
+			tofree = 1;
 			r = duplicate(r);
+		}
 		search(state.vars, lib, r);
 		append(tmp, lib + 2);
 		append(tmp, ".req");
@@ -1519,6 +1535,8 @@ require(char* lib, int dontcare)
 				}
 			}
 			fclose(f);
+			if(tofree)
+				free(r);
 			r = use(buf);
 		}
 		else if (dontcare)
@@ -1533,7 +1551,11 @@ require(char* lib, int dontcare)
 			append(tmp, "rm -f x.${!-$$}.[cox]\n");
 			append(tmp, "exit $c\n");
 			if (execute(expand(buf, use(tmp))))
+			{
+				if(tofree)
+					free(r);
 				r = "";
+			}
 		}
 		r = duplicate(r);
 		search(state.vars, lib, r);

src/cmd/ksh93/sh/init.c

@@ -1636,7 +1636,7 @@ static Namval_t *create_stat(Namval_t *np,const char *name,int flag,Namfun_t *fp
 	for(i=0; i < sp->numnodes; i++)
 	{
 		nq = nv_namptr(sp->nodes,i);
-		if((n==0||memcmp(name,nq->nvname,n)==0) && nq->nvname[n]==0)
+		if((n==0||strncmp(name,nq->nvname,n)==0) && nq->nvname[n]==0)
 			goto found;
 	}
 	nq = 0;

src/cmd/ksh93/sh/io.c

@@ -2703,7 +2703,7 @@ Sfio_t *sh_pathopen(const char *cp)
 
 int sh_isdevfd(register const char *fd)
 {
-	if(!fd || memcmp(fd,"/dev/fd/",8) || fd[8]==0)
+	if(!fd || strncmp(fd,"/dev/fd/",8) || fd[8]==0)
 		return(0);
 	for ( fd=&fd[8] ; *fd != '\0' ; fd++ )
 	{

src/cmd/ksh93/sh/name.c

@@ -1413,7 +1413,7 @@ Namval_t *nv_open(const char *name, Dt_t *root, int flags)
 	{
 		if(xp->root!=root)
 			continue;
-		if(*name==*xp->name && xp->namespace==shp->namespace && (flags&(NV_ARRAY|NV_NOSCOPE))==xp->flags && memcmp(xp->name,name,xp->len)==0 && (name[xp->len]==0 || name[xp->len]=='=' || name[xp->len]=='+'))
+		if(*name==*xp->name && xp->namespace==shp->namespace && (flags&(NV_ARRAY|NV_NOSCOPE))==xp->flags && strncmp(xp->name,name,xp->len)==0 && (name[xp->len]==0 || name[xp->len]=='=' || name[xp->len]=='+'))
 		{
 			sh_stats(STAT_NVHITS);
 			np = xp->np;

src/cmd/ksh93/sh/nvtree.c

@@ -257,7 +257,7 @@ static Namval_t *nextnode(struct nvdir *dp)
 {
 	if(dp->nextnode)
 		return((*dp->nextnode)(dp->hp,dp->root,dp->fun));
-	if(dp->len && memcmp(dp->data, dp->hp->nvname, dp->len))
+	if(dp->len && strncmp(dp->data, dp->hp->nvname, dp->len))
 		return(0);
 	return((Namval_t*)dtnext(dp->root,dp->hp));
 }
@@ -288,7 +288,7 @@ char *nv_dirnext(void *dir)
 					dp->hp = (*dp->nextnode)(np,(Dt_t*)0,dp->fun);
 			}
 			sh.last_table = last_table;
-			if(!dp->len || memcmp(cp,dp->data,dp->len)==0)
+			if(!dp->len || strncmp(cp,dp->data,dp->len)==0)
 			{
 				if((nfp=nextdisc(np)) && (nfp->disc->getval||nfp->disc->getnum) && nv_isvtree(np) && strcmp(cp,dp->data))
 					nfp = 0;

src/cmd/ksh93/sh/subshell.c

@@ -327,7 +327,7 @@ Namval_t *sh_assignok(register Namval_t *np,int add)
 		{
 			walk = root->walk?root->walk:root;
 			mpnext = dtnext(root,mp);
-			if(memcmp(name,mp->nvname,len) || mp->nvname[len]!='.')
+			if(strncmp(name,mp->nvname,len) || mp->nvname[len]!='.')
 				break;
 			nv_delete(mp,walk,NV_NOFREE);
 			*((Namval_t**)mp) = lp->child;

src/lib/libast/features/map.c

@@ -137,10 +137,13 @@ main()
 	printf("#undef	getwd\n");
 	printf("#define getwd		_ast_getwd\n");
 	printf("extern char*		getwd(char*);\n");
+#endif
+	/* use the libast glob functions rather than the native versions */
 	printf("#undef	glob\n");
 	printf("#define glob		_ast_glob\n");
 	printf("#undef	globfree\n");
 	printf("#define globfree	_ast_globfree\n");
+#if _map_libc
 	printf("#undef	memdup\n");
 	printf("#define memdup		_ast_memdup\n");
 	printf("#undef	memfatal\n");

src/lib/libast/misc/glob.c

@@ -587,7 +587,7 @@ skip:
 }
 
 int
-glob(const char* pattern, int flags, int (*errfn)(const char*, int), register glob_t* gp)
+_ast_glob(const char* pattern, int flags, int (*errfn)(const char*, int), register glob_t* gp)
 {
 	register globlist_t*	ap;
 	register char*		pat;
@@ -831,7 +831,7 @@ glob(const char* pattern, int flags, int (*errfn)(const char*, int), register gl
 }
 
 void
-globfree(glob_t* gp)
+_ast_globfree(glob_t* gp)
 {
 	if ((gp->gl_flags & GLOB_MAGIC) == GLOB_MAGIC)
 	{