Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
getname_maybe_null() - the third variant of pathname copy-in
Semantics used by statx(2) (and later *xattrat(2)): without AT_EMPTY_PATH
it's standard getname() (i.e. ERR_PTR(-ENOENT) on empty string,
ERR_PTR(-EFAULT) on NULL), with AT_EMPTY_PATH both empty string and
NULL are accepted.
Calling conventions: getname_maybe_null(user_pointer, flags) returns
* pointer to struct filename when non-empty string had been
successfully read
* ERR_PTR(...) on error
* NULL if an empty string or NULL pointer had been given
with AT_EMPTY_PATH in the flags argument.
It tries to avoid allocation in the last case; it's not always
able to do so, in which case the temporary struct filename instance
is freed and NULL returned anyway.
Fast path is inlined.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
+37
-31
+23
-7
fs/namei.c
+23
-7
fs/namei.c
···
211
211
return result;
212
212
}
213
213
214
-
struct filename *
215
-
getname_uflags(const char __user *filename, int uflags)
214
+
struct filename *getname_uflags(const char __user *filename, int uflags)
216
215
{
217
216
int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
218
217
219
218
return getname_flags(filename, flags);
220
219
}
221
220
222
-
struct filename *
223
-
getname(const char __user * filename)
221
+
struct filename *getname(const char __user * filename)
224
222
{
225
223
return getname_flags(filename, 0);
226
224
}
227
225
228
-
struct filename *
229
-
getname_kernel(const char * filename)
226
+
struct filename *__getname_maybe_null(const char __user *pathname)
227
+
{
228
+
struct filename *name;
229
+
char c;
230
+
231
+
/* try to save on allocations; loss on um, though */
232
+
if (get_user(c, pathname))
233
+
return ERR_PTR(-EFAULT);
234
+
if (!c)
235
+
return NULL;
236
+
237
+
name = getname_flags(pathname, LOOKUP_EMPTY);
238
+
if (!IS_ERR(name) && !(name->name[0])) {
239
+
putname(name);
240
+
name = NULL;
241
+
}
242
+
return name;
243
+
}
244
+
245
+
struct filename *getname_kernel(const char * filename)
230
246
{
231
247
struct filename *result;
232
248
int len = strlen(filename) + 1;
···
280
264
281
265
void putname(struct filename *name)
282
266
{
283
-
if (IS_ERR(name))
267
+
if (IS_ERR_OR_NULL(name))
284
268
return;
285
269
286
270
if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
+4
-24
fs/stat.c
+4
-24
fs/stat.c
···
326
326
{
327
327
int ret;
328
328
int statx_flags = flags | AT_NO_AUTOMOUNT;
329
-
struct filename *name;
329
+
struct filename *name = getname_maybe_null(filename, flags);
330
330
331
-
/*
332
-
* Work around glibc turning fstat() into fstatat(AT_EMPTY_PATH)
333
-
*
334
-
* If AT_EMPTY_PATH is set, we expect the common case to be that
335
-
* empty path, and avoid doing all the extra pathname work.
336
-
*/
337
-
if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
331
+
if (!name && dfd >= 0)
338
332
return vfs_fstat(dfd, stat);
339
333
340
-
name = getname_flags(filename, getname_statx_lookup_flags(statx_flags));
341
334
ret = vfs_statx(dfd, name, statx_flags, stat, STATX_BASIC_STATS);
342
335
putname(name);
343
336
···
767
774
struct statx __user *, buffer)
768
775
{
769
776
int ret;
770
-
unsigned lflags;
771
-
struct filename *name;
777
+
struct filename *name = getname_maybe_null(filename, flags);
772
778
773
-
/*
774
-
* Short-circuit handling of NULL and "" paths.
775
-
*
776
-
* For a NULL path we require and accept only the AT_EMPTY_PATH flag
777
-
* (possibly |'d with AT_STATX flags).
778
-
*
779
-
* However, glibc on 32-bit architectures implements fstatat as statx
780
-
* with the "" pathname and AT_NO_AUTOMOUNT | AT_EMPTY_PATH flags.
781
-
* Supporting this results in the uglification below.
782
-
*/
783
-
lflags = flags & ~(AT_NO_AUTOMOUNT | AT_STATX_SYNC_TYPE);
784
-
if (lflags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
779
+
if (!name && dfd >= 0)
785
780
return do_statx_fd(dfd, flags & ~AT_NO_AUTOMOUNT, mask, buffer);
786
781
787
-
name = getname_flags(filename, getname_statx_lookup_flags(flags));
788
782
ret = do_statx(dfd, name, flags, mask, buffer);
789
783
putname(name);
790
784
+10
include/linux/fs.h
+10
include/linux/fs.h
···
2766
2766
extern struct filename *getname_uflags(const char __user *, int);
2767
2767
extern struct filename *getname(const char __user *);
2768
2768
extern struct filename *getname_kernel(const char *);
2769
+
extern struct filename *__getname_maybe_null(const char __user *);
2770
+
static inline struct filename *getname_maybe_null(const char __user *name, int flags)
2771
+
{
2772
+
if (!(flags & AT_EMPTY_PATH))
2773
+
return getname(name);
2774
+
2775
+
if (!name)
2776
+
return NULL;
2777
+
return __getname_maybe_null(name);
2778
+
}
2769
2779
extern void putname(struct filename *name);
2770
2780
2771
2781
extern int finish_open(struct file *file, struct dentry *dentry,