[PATCH 4.4 124/137] ovl: use a minimal buffer in ovl_copy_xattr

Greg Kroah-Hartman
2016-02-24T04:17:12Z

From: Vito Caputo <vito.caputo@coreos.com>

commit e4ad29fa0d224d05e08b2858e65f112fd8edd4fe upstream.

Rather than always allocating the high-order XATTR_SIZE_MAX buffer
which is costly and prone to failure, only allocate what is needed and
realloc if necessary.

Fixes https://github.com/coreos/bugs/issues/489

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/overlayfs/copy_up.c | 39 +++++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 14 deletions(-)

--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -22,9 +22,9 @@

int ovl_copy_xattr(struct dentry *old, struct dentry *new)
{
- ssize_t list_size, size;
- char *buf, *name, *value;
- int error;
+ ssize_t list_size, size, value_size = 0;
+ char *buf, *name, *value = NULL;
+ int uninitialized_var(error);

if (!old->d_inode->i_op->getxattr ||
!new->d_inode->i_op->getxattr)
@@ -41,29 +41,40 @@ int ovl_copy_xattr(struct dentry *old, s
if (!buf)
return -ENOMEM;

- error = -ENOMEM;
- value = kmalloc(XATTR_SIZE_MAX, GFP_KERNEL);
- if (!value)
- goto out;
-
list_size = vfs_listxattr(old, buf, list_size);
if (list_size <= 0) {
error = list_size;
- goto out_free_value;
+ goto out;
}

for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
- size = vfs_getxattr(old, name, value, XATTR_SIZE_MAX);
+retry:
+ size = vfs_getxattr(old, name, value, value_size);
+ if (size == -ERANGE)
+ size = vfs_getxattr(old, name, NULL, 0);
+
if (size < 0) {
error = size;
- goto out_free_value;
+ break;
}
+
+ if (size > value_size) {
+ void *new;
+
+ new = krealloc(value, size, GFP_KERNEL);
+ if (!new) {
+ error = -ENOMEM;
+ break;
+ }
+ value = new;
+ value_size = size;
+ goto retry;
+ }
+
error = vfs_setxattr(new, name, value, size, 0);
if (error)
- goto out_free_value;
+ break;
}
-
-out_free_value:
kfree(value);
out:
kfree(buf);