[LU-11108] mdt_getxattr() may clobber errors from mo_xattr_get()

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.12.0
• Labels: xattr
• Severity: 3
• Assignee: John Hammond
• Reporter: John Hammond

Description

In mdt_getxattr() we have the following:

        if (valid == OBD_MD_FLXATTR) {
                const char *xattr_name = req_capsule_client_get(info->mti_pill,
                                                                &RMF_NAME);
                rc = mo_xattr_get(info->mti_env, next, buf, xattr_name);
                rc = mdt_nodemap_map_acl(info, buf->lb_buf, rc, xattr_name,
                                         NODEMAP_FS_TO_CLIENT);
        } ...

If rc is negative then when passed to the size_t size parameter of mdt_nodemap_map_acl() it becomes very large and may be replaced with -ERANGE.

static int mdt_nodemap_map_acl(struct mdt_thread_info *info, void *buf,
                               size_t size, const char *name,
                               enum nodemap_tree_type tree_type)
{
        struct lu_nodemap      *nodemap;
        struct obd_export      *exp = info->mti_exp;
        int                     rc = size;

        ENTRY;

        if (strcmp(name, XATTR_NAME_ACL_ACCESS) == 0 ||
            strcmp(name, XATTR_NAME_ACL_DEFAULT) == 0) {
                if (size > info->mti_mdt->mdt_max_ea_size ||
                     (!exp_connect_large_acl(exp) &&
                      size > LUSTRE_POSIX_ACL_MAX_SIZE_OLD))
                        GOTO(out, rc = -ERANGE);

                nodemap = nodemap_get_from_exp(exp);
                if (IS_ERR(nodemap))
                        GOTO(out, rc = PTR_ERR(nodemap));

                rc = nodemap_map_acl(nodemap, buf, size, tree_type);
                nodemap_putref(nodemap);
                if (rc < 0)
                        GOTO(out, rc);
        }
out:
        RETURN(rc);
}

I noticed this while looking at LU-11074 but this is not the underlying cause of that bug.