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Simplify cleanup on failure in realpath(3).

Browse Source 
If realpath() allocated memory for result and failed, the memory is
freed in each place where return is performed.  More, the function
needs to track the allocation status, to not free user-supplied
buffer.

Consolidate the memory handling in the wrapper, freeing the buffer if
the actual worker failed.

Reviewed by:	emaste (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D10670
This commit is contained in:
Konstantin Belousov 2017-05-15 17:34:17 +00:00
parent f81e5b2d9b
commit d933a4c06b
1 changed files with 31 additions and 44 deletions
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75
lib/libc/stdlib/realpath.c
View File

@ -47,32 +47,16 @@ __FBSDID("$FreeBSD$");
* components. Returns (resolved) on success, or (NULL) on failure,
* in which case the path which caused trouble is left in (resolved).
*/
char *
realpath(const char * __restrict path, char * __restrict resolved)
static char *
realpath1(const char *path, char *resolved)
{
struct stat sb;
char *p, *q;
size_t left_len, resolved_len, next_token_len;
unsigned symlinks;
int m;
ssize_t slen;
char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
if (path == NULL) {
errno = EINVAL;
return (NULL);
}
if (path[0] == '\0') {
errno = ENOENT;
return (NULL);
}
if (resolved == NULL) {
resolved = malloc(PATH_MAX);
if (resolved == NULL)
return (NULL);
m = 1;
} else
m = 0;
symlinks = 0;
if (path[0] == '/') {
resolved[0] = '/';
@ -83,20 +67,14 @@ realpath(const char * __restrict path, char * __restrict resolved)
left_len = strlcpy(left, path + 1, sizeof(left));
} else {
if (getcwd(resolved, PATH_MAX) == NULL) {
if (m)
free(resolved);
else {
resolved[0] = '.';
resolved[1] = '\0';
}
resolved[0] = '.';
resolved[1] = '\0';
return (NULL);
}
resolved_len = strlen(resolved);
left_len = strlcpy(left, path, sizeof(left));
}
if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
if (m)
free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
@ -125,8 +103,6 @@ realpath(const char * __restrict path, char * __restrict resolved)
if (resolved[resolved_len - 1] != '/') {
if (resolved_len + 1 >= PATH_MAX) {
if (m)
free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
@ -158,27 +134,18 @@ realpath(const char * __restrict path, char * __restrict resolved)
*/
resolved_len = strlcat(resolved, next_token, PATH_MAX);
if (resolved_len >= PATH_MAX) {
if (m)
free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
if (lstat(resolved, &sb) != 0) {
if (m)
free(resolved);
if (lstat(resolved, &sb) != 0)
return (NULL);
}
if (S_ISLNK(sb.st_mode)) {
if (symlinks++ > MAXSYMLINKS) {
if (m)
free(resolved);
errno = ELOOP;
return (NULL);
}
slen = readlink(resolved, symlink, sizeof(symlink));
if (slen <= 0 || slen >= sizeof(symlink)) {
if (m)
free(resolved);
if (slen < 0) {
/* keep errno from readlink(2) call */
} else if (slen == 0) {
@ -207,8 +174,6 @@ realpath(const char * __restrict path, char * __restrict resolved)
if (p != NULL) {
if (symlink[slen - 1] != '/') {
if (slen + 1 >= sizeof(symlink)) {
if (m)
free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
@ -218,16 +183,12 @@ realpath(const char * __restrict path, char * __restrict resolved)
left_len = strlcat(symlink, left,
sizeof(symlink));
if (left_len >= sizeof(symlink)) {
if (m)
free(resolved);
errno = ENAMETOOLONG;
return (NULL);
}
}
left_len = strlcpy(left, symlink, sizeof(left));
} else if (!S_ISDIR(sb.st_mode) && p != NULL) {
if (m)
free(resolved);
errno = ENOTDIR;
return (NULL);
}
@ -241,3 +202,29 @@ realpath(const char * __restrict path, char * __restrict resolved)
resolved[resolved_len - 1] = '\0';
return (resolved);
}
char *
realpath(const char * __restrict path, char * __restrict resolved)
{
char *m, *res;
if (path == NULL) {
errno = EINVAL;
return (NULL);
}
if (path[0] == '\0') {
errno = ENOENT;
return (NULL);
}
if (resolved != NULL) {
m = NULL;
} else {
m = resolved = malloc(PATH_MAX);
if (resolved == NULL)
return (NULL);
}
res = realpath1(path, resolved);
if (res == NULL)
free(m);
return (res);
}