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ovl: xattr filter fix

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a) ovl_need_xattr_filter() is wrong, we can have multiple lower layers
overlaid, all of which (except the lowest one) honouring the
"trusted.overlay.opaque" xattr.  So need to filter everything except the
bottom and the pure-upper layer.

b) we no longer can assume that inode is attached to dentry in
get/setxattr.

This patch unconditionally filters private xattrs to fix both of the above.
Performance impact for get/removexattrs is likely in the noise.

For listxattrs it might be measurable in pathological cases, but I very
much hope nobody cares.  If they do, we'll fix it then.

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: b96809173e ("security_d_instantiate(): move to the point prior to attaching dentry to inode")
This commit is contained in:
Miklos Szeredi 2016-06-06 16:21:37 +02:00
parent af8c34ce6a
commit b581755b1c
1 changed files with 6 additions and 20 deletions
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26
fs/overlayfs/inode.c
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@ -238,41 +238,27 @@ int ovl_setxattr(struct dentry *dentry, struct inode *inode,
return err;
}
static bool ovl_need_xattr_filter(struct dentry *dentry,
enum ovl_path_type type)
{
if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
return S_ISDIR(dentry->d_inode->i_mode);
else
return false;
}
ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
const char *name, void *value, size_t size)
{
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
struct dentry *realdentry = ovl_dentry_real(dentry);
if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
if (ovl_is_private_xattr(name))
return -ENODATA;
return vfs_getxattr(realpath.dentry, name, value, size);
return vfs_getxattr(realdentry, name, value, size);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
struct dentry *realdentry = ovl_dentry_real(dentry);
ssize_t res;
int off;
res = vfs_listxattr(realpath.dentry, list, size);
res = vfs_listxattr(realdentry, list, size);
if (res <= 0 || size == 0)
return res;
if (!ovl_need_xattr_filter(dentry, type))
return res;
/* filter out private xattrs */
for (off = 0; off < res;) {
char *s = list + off;
@ -302,7 +288,7 @@ int ovl_removexattr(struct dentry *dentry, const char *name)
goto out;
err = -ENODATA;
if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
if (ovl_is_private_xattr(name))
goto out_drop_write;
if (!OVL_TYPE_UPPER(type)) {