ash: exec: Do not allocate stack string in padvance
Upstream commit:
Date: Sat, 19 May 2018 02:39:48 +0800
exec: Do not allocate stack string in padvance
Many callers of padvance immediately free the allocated string
so this patch moves the stalloc call to the caller. Instead of
returning the allocated string, padvance now returns the length
to allocate (this may be longer than the actual string length,
even including the NUL). For the case where we would previously
return NULL, we now return -1.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash.c b/shell/ash.c
index 6505f49..e89cecf 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -2560,17 +2560,17 @@
/* ============ 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 @@
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 = p + 1;
else
*path = NULL;
- return stalloc(len);
+ return len;
}
@@ -2840,6 +2840,7 @@
char c;
struct stat statb;
int flags;
+ int len;
flags = cdopt();
dest = *argptr;
@@ -2869,9 +2870,10 @@
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 @@
} 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 @@
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 @@
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 @@
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 @@
* 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 @@
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 @@
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 @@
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) */
