From: David Howells <dhowells@redhat.com> To: Stephen Smalley <sds@tycho.nsa.gov> Cc: dhowells@redhat.com, linux-unionfs@vger.kernel.org, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/7] SELinux: Handle opening of a unioned file Date: Thu, 06 Nov 2014 12:03:33 +0000 [thread overview] Message-ID: <11463.1415275413@warthog.procyon.org.uk> (raw) In-Reply-To: <545A51CB.6070107@tycho.nsa.gov> Stephen Smalley <sds@tycho.nsa.gov> wrote: > How do we know that this union_isid will bear any relation to the actual > SID assigned to the union inode when it is created? Note that overlayfs *will* have a union inode at this point, but will just not use it for non-directories - so in this case we just use the first branch of the if-statement: + if (inode) { + isec = inode->i_security; + fsec->union_isid = isec->sid; + } ... in which case, I think that we can be fairly sure that we will have the right label. The other two cases are in case there isn't an inode - unionmount, for example. The second case is used (if I understand the flag correctly) if the superblock imposes a single label over all its inodes - so no problem there: + } else if ((sbsec->flags & SE_SBINITIALIZED) && + (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)) { + fsec->union_isid = sbsec->mntpoint_sid; + } ... The third case is the tricky one because we have to try and derive a label. I've copied the code from the inode creation - so unless the policy changes or the parent directory inode changes, I would've thought we'd be okay. > If the union inode does not already exist, when/where does it get created? For overlayfs, union inodes *have* to exist because it's a filesystem and are created at the normal times and in the normal way. They need to exist because otherwise the dentry at that point in the overlay fs would be negative and the VFS wouldn't call into the filesystem. > Also, would be good to create a common helper for use here, by > selinux_dentry_init_security(), selinux_inode_init_security(), and > may_create(). Already some seeming potential for inconsistencies there. Okay, I'll have a look at that. > > + return inode_has_perm(cred, file_inode(file), fsec->union_isid, &ad); > > Something is seriously wrong here; you are passing fsec->union_isid > where we expect a permissions bitmap / access vector. Good point. I need to call avc_has_perm() directly. I don't necessarily have an sclass, though, hmmm... David
WARNING: multiple messages have this Message-ID (diff)
From: David Howells <dhowells@redhat.com> To: Stephen Smalley <sds@tycho.nsa.gov> Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 5/7] SELinux: Handle opening of a unioned file Date: Thu, 06 Nov 2014 12:03:33 +0000 [thread overview] Message-ID: <11463.1415275413@warthog.procyon.org.uk> (raw) In-Reply-To: <545A51CB.6070107@tycho.nsa.gov> Stephen Smalley <sds@tycho.nsa.gov> wrote: > How do we know that this union_isid will bear any relation to the actual > SID assigned to the union inode when it is created? Note that overlayfs *will* have a union inode at this point, but will just not use it for non-directories - so in this case we just use the first branch of the if-statement: + if (inode) { + isec = inode->i_security; + fsec->union_isid = isec->sid; + } ... in which case, I think that we can be fairly sure that we will have the right label. The other two cases are in case there isn't an inode - unionmount, for example. The second case is used (if I understand the flag correctly) if the superblock imposes a single label over all its inodes - so no problem there: + } else if ((sbsec->flags & SE_SBINITIALIZED) && + (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)) { + fsec->union_isid = sbsec->mntpoint_sid; + } ... The third case is the tricky one because we have to try and derive a label. I've copied the code from the inode creation - so unless the policy changes or the parent directory inode changes, I would've thought we'd be okay. > If the union inode does not already exist, when/where does it get created? For overlayfs, union inodes *have* to exist because it's a filesystem and are created at the normal times and in the normal way. They need to exist because otherwise the dentry at that point in the overlay fs would be negative and the VFS wouldn't call into the filesystem. > Also, would be good to create a common helper for use here, by > selinux_dentry_init_security(), selinux_inode_init_security(), and > may_create(). Already some seeming potential for inconsistencies there. Okay, I'll have a look at that. > > + return inode_has_perm(cred, file_inode(file), fsec->union_isid, &ad); > > Something is seriously wrong here; you are passing fsec->union_isid > where we expect a permissions bitmap / access vector. Good point. I need to call avc_has_perm() directly. I don't necessarily have an sclass, though, hmmm... David
next prev parent reply other threads:[~2014-11-06 12:04 UTC|newest] Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-11-05 15:42 [PATCH 0/7] Security: Provide unioned file support David Howells 2014-11-05 15:42 ` [PATCH 1/7] Security: Provide copy-up security hooks for unioned files David Howells 2014-11-06 17:46 ` Casey Schaufler 2014-11-07 14:49 ` David Howells 2014-11-07 14:49 ` David Howells 2014-11-07 21:22 ` Paul Moore 2014-11-07 21:22 ` Paul Moore 2014-11-07 22:10 ` David Howells 2014-11-07 22:10 ` David Howells 2014-11-10 15:28 ` Paul Moore 2014-11-10 15:28 ` Paul Moore 2014-11-05 15:42 ` [PATCH 2/7] Overlayfs: Use copy-up security hooks David Howells 2014-11-07 21:39 ` Paul Moore 2014-11-07 21:39 ` Paul Moore 2014-11-07 22:05 ` David Howells 2014-11-07 22:05 ` David Howells 2014-11-10 15:45 ` Paul Moore 2014-11-10 15:45 ` Paul Moore 2014-11-05 15:42 ` [PATCH 3/7] SELinux: Stub in copy-up handling David Howells 2014-11-07 21:44 ` Paul Moore 2014-11-07 21:44 ` Paul Moore 2014-11-07 22:08 ` David Howells 2014-11-07 22:08 ` David Howells 2014-11-10 15:47 ` Paul Moore 2014-11-10 15:47 ` Paul Moore 2014-11-05 15:42 ` [PATCH 4/7] Security: Pass the union-layer file path into security_file_open() David Howells 2014-11-05 15:43 ` [PATCH 5/7] SELinux: Handle opening of a unioned file David Howells 2014-11-05 16:35 ` Stephen Smalley 2014-11-06 12:03 ` David Howells [this message] 2014-11-06 12:03 ` David Howells 2014-11-06 13:13 ` Stephen Smalley 2014-11-06 13:13 ` Stephen Smalley 2014-11-06 13:34 ` David Howells 2014-11-06 13:34 ` David Howells 2014-11-27 14:15 ` David Howells 2014-11-27 14:15 ` David Howells 2014-11-06 12:27 ` David Howells 2014-11-06 12:27 ` David Howells 2014-11-06 12:27 ` David Howells 2014-11-27 17:25 ` David Howells 2014-11-27 17:25 ` David Howells 2015-06-12 15:30 ` David Howells 2015-06-12 15:30 ` David Howells 2015-06-15 12:57 ` Stephen Smalley 2015-06-15 12:57 ` Stephen Smalley 2015-06-16 9:41 ` David Howells 2015-06-16 9:41 ` David Howells 2015-06-16 16:49 ` David Howells 2015-06-16 16:49 ` David Howells 2015-06-16 17:20 ` Stephen Smalley 2015-06-16 17:20 ` Stephen Smalley 2015-06-16 21:34 ` David Howells 2015-06-16 21:34 ` David Howells 2015-06-17 14:44 ` Stephen Smalley 2015-06-17 14:44 ` Stephen Smalley 2015-06-18 10:15 ` David Howells 2015-06-18 10:15 ` David Howells 2015-06-18 12:48 ` Stephen Smalley 2015-06-18 12:48 ` Stephen Smalley 2015-06-18 15:26 ` David Howells 2015-06-18 15:26 ` David Howells 2015-06-18 10:32 ` David Howells 2015-06-18 10:32 ` David Howells 2015-06-18 12:16 ` Stephen Smalley 2015-06-18 12:16 ` Stephen Smalley 2014-11-05 15:43 ` [PATCH 6/7] SELinux: The copy-up operation must have read permission on the lower file David Howells 2014-11-05 16:43 ` Stephen Smalley 2014-11-05 17:54 ` Stephen Smalley 2014-11-06 13:39 ` Stephen Smalley 2014-11-27 14:17 ` David Howells 2014-11-27 14:17 ` David Howells 2014-11-27 14:21 ` David Howells 2014-11-27 14:21 ` David Howells 2014-11-27 14:21 ` David Howells 2014-11-05 15:43 ` [PATCH 7/7] SELinux: Check against union and lower labels for file ops on lower files David Howells 2014-11-06 17:35 ` [PATCH 0/7] Security: Provide unioned file support Casey Schaufler 2014-11-06 17:35 ` Casey Schaufler 2014-11-06 17:58 ` David Howells 2014-11-06 17:58 ` David Howells 2014-11-06 18:40 ` Casey Schaufler 2014-11-06 18:40 ` Casey Schaufler 2014-11-07 15:21 ` David Howells 2014-11-07 15:21 ` David Howells 2014-11-07 18:54 ` Daniel J Walsh 2014-11-07 18:54 ` Daniel J Walsh 2014-11-09 1:31 ` Casey Schaufler 2014-11-09 1:31 ` Casey Schaufler 2014-11-10 13:59 ` Daniel J Walsh 2014-11-10 13:59 ` Daniel J Walsh
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