@@ -211,22 +211,38 @@ getname_flags(const char __user *filename, int flags)
return result;
}
-struct filename *
-getname_uflags(const char __user *filename, int uflags)
+struct filename *getname_uflags(const char __user *filename, int uflags)
{
int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
return getname_flags(filename, flags);
}
-struct filename *
-getname(const char __user * filename)
+struct filename *getname(const char __user * filename)
{
return getname_flags(filename, 0);
}
-struct filename *
-getname_kernel(const char * filename)
+struct filename *__getname_maybe_null(const char __user *pathname)
+{
+ struct filename *name;
+ char c;
+
+ /* try to save on allocations; loss on um, though */
+ if (get_user(c, pathname))
+ return ERR_PTR(-EFAULT);
+ if (!c)
+ return NULL;
+
+ name = getname_flags(pathname, LOOKUP_EMPTY);
+ if (!IS_ERR(name) && !(name->name[0])) {
+ putname(name);
+ name = NULL;
+ }
+ return name;
+}
+
+struct filename *getname_kernel(const char * filename)
{
struct filename *result;
int len = strlen(filename) + 1;
@@ -264,7 +280,7 @@ EXPORT_SYMBOL(getname_kernel);
void putname(struct filename *name)
{
- if (IS_ERR(name))
+ if (IS_ERR_OR_NULL(name))
return;
if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
@@ -326,18 +326,11 @@ int vfs_fstatat(int dfd, const char __user *filename,
{
int ret;
int statx_flags = flags | AT_NO_AUTOMOUNT;
- struct filename *name;
+ struct filename *name = getname_maybe_null(filename, flags);
- /*
- * Work around glibc turning fstat() into fstatat(AT_EMPTY_PATH)
- *
- * If AT_EMPTY_PATH is set, we expect the common case to be that
- * empty path, and avoid doing all the extra pathname work.
- */
- if (flags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
+ if (!name && dfd >= 0)
return vfs_fstat(dfd, stat);
- name = getname_flags(filename, getname_statx_lookup_flags(statx_flags));
ret = vfs_statx(dfd, name, statx_flags, stat, STATX_BASIC_STATS);
putname(name);
@@ -774,24 +767,11 @@ SYSCALL_DEFINE5(statx,
struct statx __user *, buffer)
{
int ret;
- unsigned lflags;
- struct filename *name;
+ struct filename *name = getname_maybe_null(filename, flags);
- /*
- * Short-circuit handling of NULL and "" paths.
- *
- * For a NULL path we require and accept only the AT_EMPTY_PATH flag
- * (possibly |'d with AT_STATX flags).
- *
- * However, glibc on 32-bit architectures implements fstatat as statx
- * with the "" pathname and AT_NO_AUTOMOUNT | AT_EMPTY_PATH flags.
- * Supporting this results in the uglification below.
- */
- lflags = flags & ~(AT_NO_AUTOMOUNT | AT_STATX_SYNC_TYPE);
- if (lflags == AT_EMPTY_PATH && vfs_empty_path(dfd, filename))
+ if (!name && dfd >= 0)
return do_statx_fd(dfd, flags & ~AT_NO_AUTOMOUNT, mask, buffer);
- name = getname_flags(filename, getname_statx_lookup_flags(flags));
ret = do_statx(dfd, name, flags, mask, buffer);
putname(name);
@@ -2766,6 +2766,16 @@ extern struct filename *getname_flags(const char __user *, int);
extern struct filename *getname_uflags(const char __user *, int);
extern struct filename *getname(const char __user *);
extern struct filename *getname_kernel(const char *);
+extern struct filename *__getname_maybe_null(const char __user *);
+static inline struct filename *getname_maybe_null(const char __user *name, int flags)
+{
+ if (!(flags & AT_EMPTY_PATH))
+ return getname(name);
+
+ if (!name)
+ return NULL;
+ return __getname_maybe_null(name);
+}
extern void putname(struct filename *name);
extern int finish_open(struct file *file, struct dentry *dentry,
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> --- fs/namei.c | 30 +++++++++++++++++++++++------- fs/stat.c | 28 ++++------------------------ include/linux/fs.h | 10 ++++++++++ 3 files changed, 37 insertions(+), 31 deletions(-)