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path-util: tighten path_extract_filename()

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Let's tighten the logic behind path_extract_filename() a bit: first of
all, refuse all cases of invalid paths with -EINVAL. More importantly
though return a recognizable error when a valid path is specified that
does not contain any filename. Specifically, "/" will now result in
-EADDRNOTAVAIL.

This changes API, but none of the existing callers care about the return
value, hence the change should be fine.
This commit is contained in:
Lennart Poettering 2021-01-25 19:50:47 +01:00 committed by Luca Boccassi
parent 23cfef7bb1
commit 3cdcbdd32f
2 changed files with 16 additions and 15 deletions
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25
src/basic/path-util.c
View file

@ -823,6 +823,8 @@ const char *last_path_component(const char *path) {
* Also, the empty string is mapped to itself.
*
* This is different than basename(), which returns "" when a trailing slash is present.
*
* This always succeeds (except if you pass NULL in which case it returns NULL, too).
*/
unsigned l, k;
@ -848,24 +850,24 @@ const char *last_path_component(const char *path) {
int path_extract_filename(const char *p, char **ret) {
_cleanup_free_ char *a = NULL;
const char *c, *e = NULL, *q;
const char *c;
/* Extracts the filename part (i.e. right-most component) from a path, i.e. string that passes
* filename_is_valid(). A wrapper around last_path_component(), but eats up trailing slashes. */
* filename_is_valid(). A wrapper around last_path_component(), but eats up trailing slashes. Returns
* -EADDRNOTAVAIL if specified parameter includes no filename (i.e. is "/" or so). Returns -EINVAL if
* not a valid path in the first place. */
if (!p)
if (!path_is_valid(p))
return -EINVAL;
/* Special case the root dir, because in that case we simply have no filename, but
* last_path_component() won't complain */
if (path_equal(p, "/"))
return -EADDRNOTAVAIL;
c = last_path_component(p);
for (q = c; *q != 0; q++)
if (*q != '/')
e = q + 1;
if (!e) /* no valid character? */
return -EINVAL;
a = strndup(c, e - c);
a = strndup(c, strcspn(c, "/"));
if (!a)
return -ENOMEM;
@ -873,7 +875,6 @@ int path_extract_filename(const char *p, char **ret) {
return -EINVAL;
*ret = TAKE_PTR(a);
return 0;
}

6
src/test/test-path-util.c
View file

@ -578,9 +578,9 @@ static void test_path_extract_filename(void) {
test_path_extract_filename_one(NULL, NULL, -EINVAL);
test_path_extract_filename_one("a/b/c", "c", 0);
test_path_extract_filename_one("a/b/c/", "c", 0);
test_path_extract_filename_one("/", NULL, -EINVAL);
test_path_extract_filename_one("//", NULL, -EINVAL);
test_path_extract_filename_one("///", NULL, -EINVAL);
test_path_extract_filename_one("/", NULL, -EADDRNOTAVAIL);
test_path_extract_filename_one("//", NULL, -EADDRNOTAVAIL);
test_path_extract_filename_one("///", NULL, -EADDRNOTAVAIL);
test_path_extract_filename_one(".", NULL, -EINVAL);
test_path_extract_filename_one("./.", NULL, -EINVAL);
test_path_extract_filename_one("././", NULL, -EINVAL);