[LU-6299] OSP does not handle zero length xattr values well

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.8.0
• Affects Version/s: Lustre 2.7.0
• Severity: 3
• Assignee: Di Wang
• Reporter: John Hammond

Description

The OSP/OUT code assumes that xattr values always have a non-zero length. For example,

static int out_xattr_set(struct tgt_session_info *tsi)
{
         ...
        buf = object_update_param_get(update, 1, &buf_len);
        if (buf == NULL || buf_len == 0) {
                CERROR("%s: empty buf for xattr set: rc = %d\n",
                       tgt_name(tsi->tsi_tgt), -EPROTO);
                RETURN(err_serious(-EPROTO));
        }
        ...

Here is what happens on 2.6.94-18-g7c82a9c

t:lustre-release# cd /mnt/lustre
t:lustre# lfs mkdir -c4 d0
t:lustre# setfattr -n user.foo d0

Message from syslogd@t at Feb 26 10:53:15 ...
 kernel:[  409.511761] LustreError: 4876:0:(osp_object.c:1132:__osp_xattr_set()) ASSERTION( buf->lb_len > 0 && buf->lb_buf != ((void *)0) ) failed: 

Message from syslogd@t at Feb 26 10:53:15 ...
 kernel:[  409.515616] LustreError: 4876:0:(osp_object.c:1132:__osp_xattr_set()) LBUG