tmpfs wants to support limited user extended attributes, but kernfs
(or cgroupfs, the only kernfs with KERNFS_ROOT_SUPPORT_USER_XATTR)
already supports user extended attributes through simple xattrs: but
limited by a policy (128KiB per inode) too liberal to be used on tmpfs.
To allow a different limiting policy for tmpfs, without affecting the
policy for kernfs, change simple_xattr_set() to return the replaced or
removed xattr (if any), leaving the caller to update their accounting
then free the xattr (by simple_xattr_free(), renamed from the static
free_simple_xattr()).
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
fs/kernfs/inode.c | 46 +++++++++++++++++++++++++---------------
fs/xattr.c | 51 +++++++++++++++++++--------------------------
include/linux/xattr.h | 7 ++++---
mm/shmem.c | 10 +++++----
4 files changed, 61 insertions(+), 53 deletions(-)
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index b22b74d1a115..fec5d5f78f07 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -306,11 +306,17 @@ int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
const void *value, size_t size, int flags)
{
+ struct simple_xattr *old_xattr;
struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
if (!attrs)
return -ENOMEM;
- return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL);
+ old_xattr = simple_xattr_set(&attrs->xattrs, name, value, size, flags);
+ if (IS_ERR(old_xattr))
+ return PTR_ERR(old_xattr);
+
+ simple_xattr_free(old_xattr);
+ return 0;
}
static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
@@ -342,7 +348,7 @@ static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
{
atomic_t *sz = &kn->iattr->user_xattr_size;
atomic_t *nr = &kn->iattr->nr_user_xattrs;
- ssize_t removed_size;
+ struct simple_xattr *old_xattr;
int ret;
if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
@@ -355,13 +361,18 @@ static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
goto dec_size_out;
}
- ret = simple_xattr_set(xattrs, full_name, value, size, flags,
- &removed_size);
-
- if (!ret && removed_size >= 0)
- size = removed_size;
- else if (!ret)
+ old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
+ if (!old_xattr)
return 0;
+
+ if (IS_ERR(old_xattr)) {
+ ret = PTR_ERR(old_xattr);
+ goto dec_size_out;
+ }
+
+ ret = 0;
+ size = old_xattr->size;
+ simple_xattr_free(old_xattr);
dec_size_out:
atomic_sub(size, sz);
dec_count_out:
@@ -376,18 +387,19 @@ static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
{
atomic_t *sz = &kn->iattr->user_xattr_size;
atomic_t *nr = &kn->iattr->nr_user_xattrs;
- ssize_t removed_size;
- int ret;
+ struct simple_xattr *old_xattr;
- ret = simple_xattr_set(xattrs, full_name, value, size, flags,
- &removed_size);
+ old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
+ if (!old_xattr)
+ return 0;
- if (removed_size >= 0) {
- atomic_sub(removed_size, sz);
- atomic_dec(nr);
- }
+ if (IS_ERR(old_xattr))
+ return PTR_ERR(old_xattr);
- return ret;
+ atomic_sub(old_xattr->size, sz);
+ atomic_dec(nr);
+ simple_xattr_free(old_xattr);
+ return 0;
}
static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
diff --git a/fs/xattr.c b/fs/xattr.c
index e7bbb7f57557..ba37a8f5cfd1 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -1040,12 +1040,12 @@ const char *xattr_full_name(const struct xattr_handler *handler,
EXPORT_SYMBOL(xattr_full_name);
/**
- * free_simple_xattr - free an xattr object
+ * simple_xattr_free - free an xattr object
* @xattr: the xattr object
*
* Free the xattr object. Can handle @xattr being NULL.
*/
-static inline void free_simple_xattr(struct simple_xattr *xattr)
+void simple_xattr_free(struct simple_xattr *xattr)
{
if (xattr)
kfree(xattr->name);
@@ -1164,7 +1164,6 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
* @value: the value to store along the xattr
* @size: the size of @value
* @flags: the flags determining how to set the xattr
- * @removed_size: the size of the removed xattr
*
* Set a new xattr object.
* If @value is passed a new xattr object will be allocated. If XATTR_REPLACE
@@ -1181,29 +1180,27 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
* nothing if XATTR_CREATE is specified in @flags or @flags is zero. For
* XATTR_REPLACE we fail as mentioned above.
*
- * Return: On success zero and on error a negative error code is returned.
+ * Return: On success, the removed or replaced xattr is returned, to be freed
+ * by the caller; or NULL if none. On failure a negative error code is returned.
*/
-int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
- const void *value, size_t size, int flags,
- ssize_t *removed_size)
+struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,
+ const char *name, const void *value,
+ size_t size, int flags)
{
- struct simple_xattr *xattr = NULL, *new_xattr = NULL;
+ struct simple_xattr *old_xattr = NULL, *new_xattr = NULL;
struct rb_node *parent = NULL, **rbp;
int err = 0, ret;
- if (removed_size)
- *removed_size = -1;
-
/* value == NULL means remove */
if (value) {
new_xattr = simple_xattr_alloc(value, size);
if (!new_xattr)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
new_xattr->name = kstrdup(name, GFP_KERNEL);
if (!new_xattr->name) {
- free_simple_xattr(new_xattr);
- return -ENOMEM;
+ simple_xattr_free(new_xattr);
+ return ERR_PTR(-ENOMEM);
}
}
@@ -1217,12 +1214,12 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
else if (ret > 0)
rbp = &(*rbp)->rb_right;
else
- xattr = rb_entry(*rbp, struct simple_xattr, rb_node);
- if (xattr)
+ old_xattr = rb_entry(*rbp, struct simple_xattr, rb_node);
+ if (old_xattr)
break;
}
- if (xattr) {
+ if (old_xattr) {
/* Fail if XATTR_CREATE is requested and the xattr exists. */
if (flags & XATTR_CREATE) {
err = -EEXIST;
@@ -1230,12 +1227,10 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
}
if (new_xattr)
- rb_replace_node(&xattr->rb_node, &new_xattr->rb_node,
- &xattrs->rb_root);
+ rb_replace_node(&old_xattr->rb_node,
+ &new_xattr->rb_node, &xattrs->rb_root);
else
- rb_erase(&xattr->rb_node, &xattrs->rb_root);
- if (!err && removed_size)
- *removed_size = xattr->size;
+ rb_erase(&old_xattr->rb_node, &xattrs->rb_root);
} else {
/* Fail if XATTR_REPLACE is requested but no xattr is found. */
if (flags & XATTR_REPLACE) {
@@ -1260,12 +1255,10 @@ int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
out_unlock:
write_unlock(&xattrs->lock);
- if (err)
- free_simple_xattr(new_xattr);
- else
- free_simple_xattr(xattr);
- return err;
-
+ if (!err)
+ return old_xattr;
+ simple_xattr_free(new_xattr);
+ return ERR_PTR(err);
}
static bool xattr_is_trusted(const char *name)
@@ -1386,7 +1379,7 @@ void simple_xattrs_free(struct simple_xattrs *xattrs)
rbp_next = rb_next(rbp);
xattr = rb_entry(rbp, struct simple_xattr, rb_node);
rb_erase(&xattr->rb_node, &xattrs->rb_root);
- free_simple_xattr(xattr);
+ simple_xattr_free(xattr);
rbp = rbp_next;
}
}
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index d591ef59aa98..e37fe667ae04 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -116,11 +116,12 @@ struct simple_xattr {
void simple_xattrs_init(struct simple_xattrs *xattrs);
void simple_xattrs_free(struct simple_xattrs *xattrs);
struct simple_xattr *simple_xattr_alloc(const void *value, size_t size);
+void simple_xattr_free(struct simple_xattr *xattr);
int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
void *buffer, size_t size);
-int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
- const void *value, size_t size, int flags,
- ssize_t *removed_size);
+struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,
+ const char *name, const void *value,
+ size_t size, int flags);
ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
char *buffer, size_t size);
void simple_xattr_add(struct simple_xattrs *xattrs,
diff --git a/mm/shmem.c b/mm/shmem.c
index 0f83d86fd8b4..df3cabf54206 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3595,15 +3595,17 @@ static int shmem_xattr_handler_set(const struct xattr_handler *handler,
size_t size, int flags)
{
struct shmem_inode_info *info = SHMEM_I(inode);
- int err;
+ struct simple_xattr *old_xattr;
name = xattr_full_name(handler, name);
- err = simple_xattr_set(&info->xattrs, name, value, size, flags, NULL);
- if (!err) {
+ old_xattr = simple_xattr_set(&info->xattrs, name, value, size, flags);
+ if (!IS_ERR(old_xattr)) {
+ simple_xattr_free(old_xattr);
+ old_xattr = NULL;
inode->i_ctime = current_time(inode);
inode_inc_iversion(inode);
}
- return err;
+ return PTR_ERR(old_xattr);
}
static const struct xattr_handler shmem_security_xattr_handler = {
--
2.35.3
