[PATCH AUTOSEL 4.19 18/47] ceph: fix listxattr vxattr buffer length calculation

Sasha Levin
2019-07-26T13:54:49Z

From: David Disseldorp <ddiss@suse.de>

[ Upstream commit 2b2abcac8c251d1c77a4cc9d9f248daefae0fb4e ]

ceph_listxattr() incorrectly returns a length based on the static
ceph_vxattrs_name_size() value, which only takes into account whether
vxattrs are hidden, ignoring vxattr.exists_cb().

When filling the xattr buffer ceph_listxattr() checks VXATTR_FLAG_HIDDEN
and vxattr.exists_cb(). If both are false, we return an incorrect
(oversize) length.

Fix this behaviour by always calculating the vxattrs length at runtime,
taking both vxattr.hidden and vxattr.exists_cb() into account.

This bug is only exposed with the new "ceph.snap.btime" vxattr, as all
other vxattrs with a non-null exists_cb also carry VXATTR_FLAG_HIDDEN.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ceph/xattr.c | 54 +++++++++++++++++++++++++++----------------------
1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 5cc8b94f8206..996ee87b1eaf 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -879,10 +879,9 @@ ssize_t ceph_listxattr(struct dentry *dentry, char *names, size_t size)
struct inode *inode = d_inode(dentry);
struct ceph_inode_info *ci = ceph_inode(inode);
struct ceph_vxattr *vxattrs = ceph_inode_vxattrs(inode);
- u32 vir_namelen = 0;
+ bool len_only = (size == 0);
u32 namelen;
int err;
- u32 len;
int i;

spin_lock(&ci->i_ceph_lock);
@@ -901,38 +900,45 @@ ssize_t ceph_listxattr(struct dentry *dentry, char *names, size_t size)
err = __build_xattrs(inode);
if (err < 0)
goto out;
- /*
- * Start with virtual dir xattr names (if any) (including
- * terminating '\0' characters for each).
- */
- vir_namelen = ceph_vxattrs_name_size(vxattrs);

- /* adding 1 byte per each variable due to the null termination */
+ /* add 1 byte for each xattr due to the null termination */
namelen = ci->i_xattrs.names_size + ci->i_xattrs.count;
- err = -ERANGE;
- if (size && vir_namelen + namelen > size)
- goto out;
-
- err = namelen + vir_namelen;
- if (size == 0)
- goto out;
+ if (!len_only) {
+ if (namelen > size) {
+ err = -ERANGE;
+ goto out;
+ }
+ names = __copy_xattr_names(ci, names);
+ size -= namelen;
+ }

- names = __copy_xattr_names(ci, names);

/* virtual xattr names, too */
- err = namelen;
if (vxattrs) {
for (i = 0; vxattrs[i].name; i++) {
- if (!(vxattrs[i].flags & VXATTR_FLAG_HIDDEN) &&
- !(vxattrs[i].exists_cb &&
- !vxattrs[i].exists_cb(ci))) {
- len = sprintf(names, "%s", vxattrs[i].name);
- names += len + 1;
- err += len + 1;
+ size_t this_len;
+
+ if (vxattrs[i].flags & VXATTR_FLAG_HIDDEN)
+ continue;
+ if (vxattrs[i].exists_cb && !vxattrs[i].exists_cb(ci))
+ continue;
+
+ this_len = strlen(vxattrs[i].name) + 1;
+ namelen += this_len;
+ if (len_only)
+ continue;
+
+ if (this_len > size) {
+ err = -ERANGE;
+ goto out;
}
+
+ memcpy(names, vxattrs[i].name, this_len);
+ names += this_len;
+ size -= this_len;
}
}
-
+ err = namelen;
out:
spin_unlock(&ci->i_ceph_lock);
return err;
--
2.20.1