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b0d2dc7d6

Denys Vlasenko

2020-02-17

SUCCESS Duration: 152s

Subject

ash: exec: Do not allocate stack string in padvance

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

shell/ash.c +38 -36

shell/ash.c+38 -36

@@ -2560,17 +2560,17 @@ listvars(int on, int off, struct strlist lp, char **end)
	/* ============ Path search helper
	*
	* The variable path (passed by reference) should be set to the start
-	* of the path before the first call; path_advance will update
-	* this value as it proceeds. Successive calls to path_advance will return
+	* of the path before the first call; padvance will update
+	* this value as it proceeds. Successive calls to padvance will return
	* the possible path expansions in sequence. If an option (indicated by
	* a percent sign) appears in the path entry then the global variable
	* pathopt will be set to point to it; otherwise pathopt will be set to
	* NULL.
	*/
-	static const char pathopt; / set by path_advance */
+	static const char pathopt; / set by padvance */

-	static char *
-	path_advance(const char *path, const char name)
+	static int
+	padvance(const char *path, const char name)
	{
	const char *p;
	char *q;
@@ -2578,7 +2578,7 @@ path_advance(const char *path, const char name)
	size_t len;

	if (*path == NULL)
-	return NULL;
+	return -1;
	start = *path;
	for (p = start; p && p != ':' && *p != '%'; p++)
	continue;
@@ -2599,7 +2599,7 @@ path_advance(const char *path, const char name)
	*path = p + 1;
	else
	*path = NULL;
-	return stalloc(len);
+	return len;
	}


@@ -2840,6 +2840,7 @@ cdcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
	char c;
	struct stat statb;
	int flags;
+	int len;

	flags = cdopt();
	dest = *argptr;
@@ -2869,9 +2870,10 @@ cdcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
	if (!*dest)
	dest = ".";
	path = bltinlookup("CDPATH");
-	while (path) {
-	c = *path;
-	p = path_advance(&path, dest);
+	while (p = path, (len = padvance(&path, dest)) >= 0) {
+	c = *p;
+	p = stalloc(len);
+
	if (stat(p, &statb) >= 0 && S_ISDIR(statb.st_mode)) {
	if (c && c != ':')
	flags \|= CD_PRINT;
@@ -8169,13 +8171,13 @@ static void shellexec(char prog, char argv, const char path, int idx)
	} else {
	try_PATH:
	e = ENOENT;
-	while ((cmdname = path_advance(&path, prog)) != NULL) {
+	while (padvance(&path, argv[0]) >= 0) {
+	cmdname = stackblock();
	if (--idx < 0 && pathopt == NULL) {
	tryexec(IF_FEATURE_SH_STANDALONE(-1,) cmdname, argv, envp);
	if (errno != ENOENT && errno != ENOTDIR)
	e = errno;
	}
-	stunalloc(cmdname);
	}
	}

@@ -8208,9 +8210,9 @@ printentry(struct tblentry *cmdp)
	idx = cmdp->param.index;
	path = pathval();
	do {
-	name = path_advance(&path, cmdp->cmdname);
-	stunalloc(name);
+	padvance(&path, cmdp->cmdname);
	} while (--idx >= 0);
+	name = stackblock();
	out1fmt("%s%s\n", name, (cmdp->rehash ? "*" : nullstr));
	}

@@ -8603,9 +8605,9 @@ describe_command(char command, const char path, int describe_command_verbose)
	p = command;
	} else {
	do {
-	p = path_advance(&path, command);
-	stunalloc(p);
+	padvance(&path, command);
	} while (--j >= 0);
+	p = stackblock();
	}
	if (describe_command_verbose) {
	out1fmt(" is %s", p);
@@ -11020,8 +11022,12 @@ chkmail(void)
	mpath = mpathset() ? mpathval() : mailval();
	new_hash = 0;
	for (;;) {
-	p = path_advance(&mpath, nullstr);
-	if (p == NULL)
+	int len;
+
+	len = padvance(&mpath, nullstr);
+	if (!len)
+	break;
+	p = stackblock();
	break;
	if (*p == '\0')
	continue;
@@ -13341,33 +13347,30 @@ cmdloop(int top)
	* search for the file, which is necessary to find sub-commands.
	*/
	static char *
-	find_dot_file(char *name)
+	find_dot_file(char *basename)
	{
	char *fullname;
	const char *path = pathval();
	struct stat statb;
+	int len;

	/* don't try this for absolute or relative paths */
-	if (strchr(name, '/'))
-	return name;
+	if (strchr(basename, '/'))
+	return basename;

-	while ((fullname = path_advance(&path, name)) != NULL) {
+	while ((len = padvance(&path, basename)) >= 0) {
+	fullname = stackblock();
	if ((stat(fullname, &statb) == 0) && S_ISREG(statb.st_mode)) {
-	/*
-	* Don't bother freeing here, since it will
-	* be freed by the caller.
-	*/
-	return fullname;
+	/* This will be freed by the caller. */
+	return stalloc(len);
	}
-	if (fullname != name)
-	stunalloc(fullname);
	}
	/* not found in PATH */

	#if ENABLE_ASH_BASH_SOURCE_CURDIR
-	return name;
+	return basename;
	#else
-	ash_msg_and_raise_error("%s: not found", name);
+	ash_msg_and_raise_error("%s: not found", basename);
	/* NOTREACHED */
	#endif
	}
@@ -13470,6 +13473,7 @@ find_command(char name, struct cmdentry entry, int act, const char *path)
	int e;
	int updatetbl;
	struct builtincmd *bcmd;
+	int len;

	/* If name contains a slash, don't use PATH or hash table */
	if (strchr(name, '/') != NULL) {
@@ -13561,10 +13565,8 @@ find_command(char name, struct cmdentry entry, int act, const char *path)
	e = ENOENT;
	idx = -1;
	loop:
-	while ((fullname = path_advance(&path, name)) != NULL) {
-	stunalloc(fullname);
-	/* NB: code below will still use fullname
-	* despite it being "unallocated" */
+	while ((len = padvance(&path, name)) >= 0) {
+	fullname = stackblock();
	idx++;
	if (pathopt) {
	if (prefix(pathopt, "builtin")) {
@@ -13598,7 +13600,7 @@ find_command(char name, struct cmdentry entry, int act, const char *path)
	if (!S_ISREG(statb.st_mode))
	continue;
	if (pathopt) { /* this is a %func directory */
-	stalloc(strlen(fullname) + 1);
+	stalloc(len);
	/* NB: stalloc will return space pointed by fullname
	* (because we don't have any intervening allocations
	* between stunalloc above and this stalloc) */