On Wed, 2019-06-12 at 21:51 +0800, Yan, Zheng wrote:
On Sat, Jun 8, 2019 at 2:47 AM Jeff Layton
<jlayton(a)kernel.org> wrote:
We have several virtual xattrs in cephfs which
return various values as
strings. xattrs don't necessarily return strings however, so we need to
include the terminating NULL byte when we return the length.
Furthermore, the getxattr manpage says that we should return -ERANGE if
the buffer is too small to hold the resulting value. Let's start doing
that here as well.
URL:
https://bugzilla.redhat.com/show_bug.cgi?id=1717454
Reported-by: Tomas Petr <tpetr(a)redhat.com>
Signed-off-by: Jeff Layton <jlayton(a)kernel.org>
---
fs/ceph/xattr.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 6621d27e64f5..2a61e02e7166 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -803,8 +803,15 @@ ssize_t __ceph_getxattr(struct inode *inode, const char *name, void
*value,
if (err)
return err;
err = -ENODATA;
- if (!(vxattr->exists_cb && !vxattr->exists_cb(ci)))
- err = vxattr->getxattr_cb(ci, value, size);
+ if (!(vxattr->exists_cb && !vxattr->exists_cb(ci))) {
+ /*
+ * getxattr_cb returns strlen(value), xattr length must
+ * include the NULL.
+ */
+ err = vxattr->getxattr_cb(ci, value, size) + 1;
This confuses getfattr. also causes failures of our test cases.
run getfattr without the patch, we get:
[root@kvm2-alpha ceph]# getfattr -n ceph.dir.entries .
# file: .
ceph.dir.entries="1"
with the patch, we get
[root@kvm1-alpha ceph]# getfattr -n ceph.dir.entries .
# file: .
ceph.dir.entries=0sMQA=
(cc'ing Andreas...)
I have to wonder if this is a bug in getfattr. If I do this, then it
works:
$ getfattr -e text -n ceph.dir.entries .
# file: .
ceph.dir.entries="1"
...which makes me think that we're running afoul of
well_enough_printable() in getfattr command.
When I set a "user." xattr to a (short) string, it doesn't include the
null terminator. security.selinux however, does include the NULL
terminating byte in the returned length. I guess though, that it's
returning long enough strings that well_enough_printable returns true.
Andreas, we have a number of "virtual" xattrs in cephfs. When we're
returning xattr values that are strings, should the returned length
include the NULL terminating byte?
> + if (size && size
< err)
> + err = -ERANGE;
> + }
> return err;
> }
>
> --
> 2.21.0
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Thanks,
--
Jeff Layton <jlayton(a)kernel.org>