Commit 7950e385 authored by Jeff Layton's avatar Jeff Layton Committed by Al Viro

vfs: embed struct filename inside of names_cache allocation if possible

In the common case where a name is much smaller than PATH_MAX, an extra
allocation for struct filename is unnecessary. Before allocating a
separate one, try to embed the struct filename inside the buffer first. If
it turns out that that's not long enough, then fall back to allocating a
separate struct filename and redoing the copy.
Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent adb5c247
...@@ -119,40 +119,69 @@ ...@@ -119,40 +119,69 @@
*/ */
void final_putname(struct filename *name) void final_putname(struct filename *name)
{ {
if (name->separate) {
__putname(name->name); __putname(name->name);
kfree(name); kfree(name);
} else {
__putname(name);
}
} }
#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
static struct filename * static struct filename *
getname_flags(const char __user *filename, int flags, int *empty) getname_flags(const char __user *filename, int flags, int *empty)
{ {
struct filename *result, *err; struct filename *result, *err;
char *kname;
int len; int len;
long max;
char *kname;
result = audit_reusename(filename); result = audit_reusename(filename);
if (result) if (result)
return result; return result;
/* FIXME: create dedicated slabcache? */ result = __getname();
result = kzalloc(sizeof(*result), GFP_KERNEL);
if (unlikely(!result)) if (unlikely(!result))
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
kname = __getname(); /*
if (unlikely(!kname)) { * First, try to embed the struct filename inside the names_cache
err = ERR_PTR(-ENOMEM); * allocation
goto error_free_name; */
} kname = (char *)result + sizeof(*result);
result->name = kname; result->name = kname;
result->uptr = filename; result->separate = false;
len = strncpy_from_user(kname, filename, PATH_MAX); max = EMBEDDED_NAME_MAX;
recopy:
len = strncpy_from_user(kname, filename, max);
if (unlikely(len < 0)) { if (unlikely(len < 0)) {
err = ERR_PTR(len); err = ERR_PTR(len);
goto error; goto error;
} }
/*
* Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
* separate struct filename so we can dedicate the entire
* names_cache allocation for the pathname, and re-do the copy from
* userland.
*/
if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
kname = (char *)result;
result = kzalloc(sizeof(*result), GFP_KERNEL);
if (!result) {
err = ERR_PTR(-ENOMEM);
result = (struct filename *)kname;
goto error;
}
result->name = kname;
result->separate = true;
max = PATH_MAX;
goto recopy;
}
/* The empty path is special. */ /* The empty path is special. */
if (unlikely(!len)) { if (unlikely(!len)) {
if (empty) if (empty)
...@@ -163,15 +192,15 @@ getname_flags(const char __user *filename, int flags, int *empty) ...@@ -163,15 +192,15 @@ getname_flags(const char __user *filename, int flags, int *empty)
} }
err = ERR_PTR(-ENAMETOOLONG); err = ERR_PTR(-ENAMETOOLONG);
if (likely(len < PATH_MAX)) { if (unlikely(len >= PATH_MAX))
goto error;
result->uptr = filename;
audit_getname(result); audit_getname(result);
return result; return result;
}
error: error:
__putname(kname); final_putname(result);
error_free_name:
kfree(result);
return err; return err;
} }
......
...@@ -2201,6 +2201,7 @@ struct filename { ...@@ -2201,6 +2201,7 @@ struct filename {
const char *name; /* pointer to actual string */ const char *name; /* pointer to actual string */
const __user char *uptr; /* original userland pointer */ const __user char *uptr; /* original userland pointer */
struct audit_names *aname; struct audit_names *aname;
bool separate; /* should "name" be freed? */
}; };
extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs, extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
......
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