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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=1jCh94g6oZvKC5v97eK4sFOl++geGsWjx4TERsIiFmo=; b=LaSY0qX6SaGv3XPhh7wptWsxc1OJDVF4RTorB9r46sJXZErX2nXScTttVMWonuZ/oR4W7Spis/Ph2KkrDwO7Mvtliqyo2R2PL9/ZChp56ktztLlzpI0X0gWnwIo4uOXQJGME+Cu9FjIUbVEeEleyj9TuL14C8CdkfOMEtcexfWU= Subject: Re: [PATCH] common: don't require use of DOMID_SELF To: Jan Beulich , "xen-devel@lists.xenproject.org" CC: George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu References: <72c9f0ec-81e3-63f9-2513-46e463642219@suse.com> From: Andrew Cooper Message-ID: <3c0ebca6-a5e9-36a8-cfeb-6abc0fc7c2af@citrix.com> Date: Thu, 14 Jan 2021 15:01:07 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <72c9f0ec-81e3-63f9-2513-46e463642219@suse.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?emxvVmZySjRvQzdQczFtaFdGVjh4RmZVdzJQR3U4SkFod1c0ME5BaW1yb0Ns?= =?utf-8?B?MDZMdUdBeUFVVmVsdjRacGVwR25taTQybnpHeE5QQU1scFhTZWNMQ2tmTWlP?= =?utf-8?B?NlNkaHBENXJvM1g1eG8ralZDRmE4WEJucVdnMzRPc0RKSTF2eDdiYlA0dkND?= =?utf-8?B?VUlIZmprY1J5Q2RnYWlNd0wrVTMwamFabFAyOTROMDM0bHphYStKUUoxYmNK?= =?utf-8?B?ejJ3K1BDa3NYcUtCNE5pNUpLMGpKYWxHSDB1WTYrTTFDdE03UmxqRDUvcGVo?= =?utf-8?B?ZWNPd1BmWk1velE0aHlwUXlaY2xYN2o1bW5weEFXYXM2bWtzSXpqQUNxRTla?= =?utf-8?B?MDFpZFdyVkNmNHluMVd4QmFoMUd1eXk4cXd5OVEvVlJyM2hGRVZiV3JHVVli?= =?utf-8?B?SjRSTFQ3VW9vR083VXMwNHVoRnZnOFFHaHpKaVk2YTRSMkdNS0VQU1dvZUN3?= =?utf-8?B?QlVab2FRRytBeUFMUzBuRnpjd01qSkxBRGdaa05nUWlqTktXUDZZSDJWdkNM?= =?utf-8?B?MXk2UUM5UzdxRll3cHJiclhLNnhHNUxSQjlnSXluWnhqMHlPTHZoMTdBdWcy?= =?utf-8?B?Zk9UeVNtUDFTM1FUVnpWVjdWenFGZFZCVmMxZ0dlVFg1dDhiYzZsVURXM3U0?= =?utf-8?B?ZmNLYW1nWEtrcmxvSUx2NzVoVmNPMTJGVW5CMExtK1VKdnM5S05hMHFEcXdz?= =?utf-8?B?RDg0N1hZTmRDVmk4ZFNjeHoxUndEZFYxNjVPVXlNcDE3NllxRHR3RnFHcURm?= =?utf-8?B?TWFBOTduT0tyVjdySk41dllxYURlZDVkMDVJWGp3eFMwZlBUY2dZMFpHZFNE?= =?utf-8?B?Y3dPNlU4dnFMTGZZOEJWdzhvaGdJMVgxNEYwUm05V3YwbTlMNmlBVFoxaVZq?= =?utf-8?B?VTNWTHZDUUZHOEw4emlwOXBSdlMybWl0V3VVcTFPVUZqY1BTbTVhbGdGYnVs?= =?utf-8?B?Wm9uSWZta1YzV1JzZm14RWJxV3J0WGlUaWpoVGgyclRHOWdwZlVuVUl2WlZu?= =?utf-8?B?RWJKaHhQend5ZDk0dmprd3JQQnJyQUpacHhtb2NvUk9uMnlMTzF1c0xiVmRh?= =?utf-8?B?VFdBU05KOUlPU2J4SFJHVlM0TzVWMGV3UjdNbkpOYkQ2WEhLRk05b0RoY2dN?= =?utf-8?B?eFQ3K3dRYnJ4VCtCZkFvc0wwZklFeWwvYi91YjRNVzJaYTduOVlpd3NxTFdu?= =?utf-8?B?QkxMYkVFVjZTQUhLZ1hQNTVXRUgvMk5qRDdoNnllbjZLb0VYOXk5SnprRkIv?= =?utf-8?B?ZlA3cHdvUjhSRDc2d284b2lHenlqYkVrRDlXL2wxM0pRcmpFdWhQeFVMYi9D?= =?utf-8?Q?0n0uobAa9r+IG3dmmrySWRc/b7Lzm/sQi+?= X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB4728.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jan 2021 15:01:14.8681 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-Network-Message-Id: 50a46167-84f9-4fb9-77c9-08d8b89d3d3f X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ZcTIfuW2e2a12cTGokHBgnCMlzCaGTxrjnBtqv4y1jzHpsHSH6XfWK10BQW2/alJ+/TTRLQ0tvhLaPojDoM2lmald8saK+KNFfYG45tbdLw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR03MB5127 X-OriginatorOrg: citrix.com On 14/01/2021 14:02, Jan Beulich wrote: > It's not overly difficult for a domain to figure out its ID, so > requiring the use of DOMID_SELF in a very limited set of places isn't > really helpful towards keeping the ID opaque to the guest. > > Signed-off-by: Jan Beulich > > --- a/xen/common/grant_table.c > +++ b/xen/common/grant_table.c > @@ -2776,15 +2776,19 @@ struct gnttab_copy_buf { > static int gnttab_copy_lock_domain(domid_t domid, bool is_gref, > struct gnttab_copy_buf *buf) > { > - /* Only DOMID_SELF may reference via frame. */ > - if ( domid != DOMID_SELF && !is_gref ) > - return GNTST_permission_denied; > - > buf->domain = rcu_lock_domain_by_any_id(domid); > > if ( !buf->domain ) > return GNTST_bad_domain; > > + /* Only the local domain may reference via frame. */ > + if ( buf->domain != current->domain && !is_gref ) > + { > + rcu_unlock_domain(buf->domain); > + buf->domain = NULL; > + return GNTST_permission_denied; > + } In this case, it's also a weird asymmetry where this is one grant table operation which a privileged domain can't issue on behalf of an unprivileged one. > + > buf->ptr.domid = domid; > > return GNTST_okay; > --- a/xen/common/page_alloc.c > +++ b/xen/common/page_alloc.c > @@ -2566,13 +2566,7 @@ __initcall(register_heap_trigger); > > struct domain *get_pg_owner(domid_t domid) > { > - struct domain *pg_owner = NULL, *curr = current->domain; > - > - if ( unlikely(domid == curr->domain_id) ) > - { > - gdprintk(XENLOG_WARNING, "Cannot specify itself as foreign domain\n"); > - goto out; > - } > + struct domain *pg_owner; I'm not sure this is correct. It isn't a DOMID_SELF check.  It's a "confirm the nominated domid is remote" check, and I don't see all the callers of this interface having appropriate checks to prohibit trying to do a foreign operation on oneself, however they specify the foreign domid. ~Andrew